# Reference Request: Human visual system takes in \$10^7\$ bits/sec at the periphery and compresses it down to 50 bits/sec deep inside

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In Sparse Components of Images and Optimal Atomic Decompositions by Donoho, 1998, the author claims that

The human visual system is thought to do a tremendous job in achieving sparse representation of image data, taking $$10^7$$ bits/sec at the periphery of the visual pathway and winnowing it down to about 50 bits/sec deep inside.

Can somebody please point me to the source of that claim, as it is not mentioned in the paper, at least to my knowledge.

The original link in the Abstract referenced (https://link.springer.com/content/pdf/10.1007%2F978-3-642-04954-5_7.pdf) above isn't available anymore, but I found a repository:

https://webdav.tuebingen.mpg.de/u/zli/prints/ZhaopingNReview2006.pdf

I don't think the review is peer reviewed, but maybe you find a reference in there (it's not my field, so I guess you know more on where to look ;-)

She's now in Germany: https://www.researchgate.net/profile/Li_Zhaoping

If you don't find anything, maybe you can ask her on researchgate directly.

## Fundamental bound on the persistence and capacity of short-term memory stored as graded persistent activity

It is widely believed that persistent neural activity underlies short-term memory. Yet, as we show, the degradation of information stored directly in such networks behaves differently from human short-term memory performance. We build a more general framework where memory is viewed as a problem of passing information through noisy channels whose degradation characteristics resemble those of persistent activity networks. If the brain first encoded the information appropriately before passing the information into such networks, the information can be stored substantially more faithfully. Within this framework, we derive a fundamental lower-bound on recall precision, which declines with storage duration and number of stored items. We show that human performance, though inconsistent with models involving direct (uncoded) storage in persistent activity networks, can be well-fit by the theoretical bound. This finding is consistent with the view that if the brain stores information in patterns of persistent activity, it might use codes that minimize the effects of noise, motivating the search for such codes in the brain.

## Behavior *

Behavior reflects nervous system activity and is dependent on multiple factors including external stimuli, past experience, neuronal structure and changes in the internal milieu of the animal. Alterations at the cellular or functional level can profoundly alter basal and evoked activity. Therefore, behavioral assays offer the researcher simple, sensitive and powerful tools to interrogate neuronal function. The sensitivity of behavioral assays can also be their greatest weakness the behavior of animals can be dramatically affected by small changes or variations in culture or assay conditions. In this short introduction, basic considerations for behavioral assays are very briefly examined. Both general considerations and admonitions relevant to C. elegans behavioral assays are included. Specific protocols for behavioral assays contributed by individual researchers follow this more general introduction.

New behavioral assays are constantly under development and old assays are often revised. Your suggestions, comments and new assays are welcome as this chapter and the appended protocols will be updated on a regular basis.

### 1.1. Considerations for behavioral assays

In the following section various parameters that contribute to behavioral response are described. Not every variable will affect every behavior. But, when troubleshooting or designing an assay, these variables should at least be considered.

### 1.2. Controls for behavioral assays

Controls: Clearly, controls are absolutely essential for all behavioral experiments. Because responses can vary from day to day it is important for control assays with appropriate strains or animals to be run every day in parallel with experimental animals. Both negative and positive controls should be tested daily. One way is to alternate control and experimental trials to control for extraneous variables. For example, a wild type C. elegans strain (N2) and a defective strain ( glr-1 ) should be tested for nose touch response in addition to any experimental strains under evaluation each day. These daily controls are reported in the literature as control results along with the corresponding experimental results.

The results of an experiment can be subtly or dramatically changed by the expectations or bias of the researcher observing the behavior. Experimenter bias is usually subconscious and exists despite the best intentions of researchers determined vigilance as to appropriate controls is required. Clearly, this entails considerable effort in both experimental design and daily effort. Ideally, all strains or animals will be scored in the behavioral assay by an observer ignorant as to the genotype, treatment and/or expected outcome. Animals or strains should be renamed and assigned code numbers prior to the experiment by another researcher to avoid bias in scoring. In some cases, only a subset of the animals is scored under these most rigorous conditions. These results of these behavioral assays are subjected to statistical analysis independent of animals tested under less rigorous conditions. If the results from the two groups are statistically equivalent, then all of the data can be pooled for reporting in the literature at the discretion of the authors and with the concordance of the reviewers. Note that these two groups of data may need to be reported independently in “Supplementary Information” for each assay.

Control strains should be raised in parallel under identical conditions this can go beyond just raising animals on the same batch of NGM plates with the same bacteria in the same box in the same incubator. Consider the controls required for behavioral assessment of animals after laser surgery. “Mock ablated” animals of the same genotype and larval stage should also be anesthetized on azide pads for the same time interval as “ablated” animals. Both “mock ablated” and “ablated” animals should be coded before behavioral testing as individual animals, not as groups of animals. This coding avoids experimenter bias toward a specific group of animals. Additional control animals (i.e. negative and positive controls) are also evaluated in parallel with the coded ablated animals to confirm that assay conditions are appropriate. The animals should also be examined to confirm that the laser microsurgery was successful prior to “decoding” the results.

Selecting the correct control animals is crucial. In the evaluation of transgenic strains, the correct control is usually not the N2 wild type strain nor is it “non-transgenic” animals from the same plate. A more appropriate control is the scoring of several independent transgenic strains generated in parallel using 1) the same transgenic marker such as GFP or phenotypic rescue, 2) the same genetic background, 3) an “empty” version of the promoter used to drive the transgene of interest and 4) that are generated by microinjection by the same experimenter. This helps decrease the corresponding problems of genetic background, marker effects on behavior, promoter copy number, and relative gene dosage. “Non-transgenic” animals from the same plate are rarely used as controls because of the mosaic nature of animals carrying extrachromosomal arrays. Unless a cell-specific marker is used to mark a specific cell of interest, “non-transgenic” animals that do not express the transgenic marker may still maintain the array and express the transgene under analysis in other behaviorally relevant cells. Strains in different labs can suffer from genetic drift resulting in altered behavior. If a transgenic strain or mutant strain is obtained from another laboratory, it is a good idea to obtain the corresponding background strain from the same laboratory.

Behavioral assessments should be made by more than one observer, should be repeated several times, and should occur on more than one day. Using more than one observer helps to avoid subconscious bias. Repeating the behavioral assay multiple times and on more than one day ensures reproducibility and consistency. Alternatively, videotaping or other optical recording of behavioral experiments permits multiple researchers to score the behavior.

### 1.3. Feeding status and cultivation conditions

Cultivation: C. elegans are generally raised on OP50 bacterial lawns on NGM agar plates. Altering the size of the lawn, the type of bacteria, the agar, and the chemicals in the NGM can affect behavioral response. Unless carefully sealed, agar plates and their bacterial lawns lose water to the atmosphere over time. Very dry culture plates should be avoided. Contamination on the culture plates can also dramatically affect behavior. Animals from contaminated plates should not be used for behavioral assays the short cut of letting contaminated animals feed on uncontaminated plates prior to the behavioral assay is not recommended. As a general rule, mold is less deleterious than yeast or bacterial contamination, but both should be avoided depending on the assay in question. A simple bleaching protocol is sufficient to generate uncontaminated animals whose offspring can be used for behavioral assays.

Crowding and feeding status: The crowding and feeding status of animals can dramatically or subtly affect behavior. For example, animals from crowded plates perform poorly in many avoidance assays. Animals clearly behave differently depending on their feeding status and history. Animals that have been starved during development or animals that have not gone through the dauer stage can have altered behavior compared to animals that have never been crowded. Feeding status also alters behavior. Animals on the bacterial lawn respond differently in behavioral assays compared to animals off the lawn. Along the same lines, increasing time off food alters behavior.

### 1.4. Ambient conditions and chemicals

Ambient conditions: The conditions under which assays occur can also affect the results of behavioral assays. Possible environmental factors that can be controlled include room humidity, temperature, drafts, and vibration. The dryness of assay plates can shift response. Some behavioral assays are more sensitive to this than others. Osmolarity and spontaneous reversal rate assays are quite sensitive to plate dryness. Depending on the assay, this can be controlled by pouring plates fresh daily, weighing plates poured at equal volume, or running controls on the same plates.

Ambient conditions (time of day, temperature and humidity) should always be recorded, so their effect can be considered when evaluating data or troubleshooting.

Some behavioral assays are run with plate lids on some with lids off.

The number of animals used in population assays can affect the outcome this should also be standardized. For example, introducing too many animals into the circular osmotic barrier used in the classical osmotic avoidance assays can result in crowding and the escape of normally defective animals.

Chemicals: The results of behavioral assays can be dramatically different depending on reagent freshness, purity and supplier. Some chemicals must be made up fresh or diluted on the day of the assay. And, impurities in chemicals (e.g., switching from a 99% pure to a 95% pure chemical) or changing suppliers can alter behavioral results. These caveats apply both to the reagents used for cultivation of the animals and the reagents used in the actual behavioral assays.

Assessing the effect of drugs and other pharmacologically active compounds on behavior involves several more variables. In addition to the preceding admonitions, the stability of the drug, the effect of any solvent, batch-to-batch variation in activity, and the actual concentration of the drug in the assay or assay plate should be considered. Control animals and plates should be treated exactly in parallel. For example, if the drug is dissolved in ethanol and then diluted in water, then the control animals or plates should be treated with the same diluted ethanol solution (lacking the drug). Note that increased osmolarity in the behavioral assay due to inclusion of the drug may alter behavior in some assays.

### 1.5. Animals to assay

Stage of life cycle: The sex, age and life cycle stage of the animal tested in an assay is an important factor for behavior. Males are generally used only for assessment of male-specific behaviors. All animals demonstrate lethargic behavior during each molt staging of young adults is unambiguous so adult hermaphrodites are generally used in assays. The stage of the life cycle can alter behavior in hermaphrodites although many assays can be used on larval animals. Nervous system development is largely complete by the end of the L1 stage, but some developmental changes are clearly coordinated with the L4/adult molt.

Behavioral changes occur during adult stages as well. Some assays are indiscriminate as to the age of the adult, but other behavioral assays are more sensitive. The age of animals can be standardized by “hours after molt to adulthood”, by hours since an egg was laid at a specified temperature, or by the number of eggs in the uterus. The former is preferable in most cases. Animals can also become less responsive to some sensory stimuli after several days of adulthood. Some researchers run behavioral assays only on animals from synchronized plates where adult hermaphrodites laid eggs over a two hour period (and then the parents were removed) to keep animal age constant.

The treatment of animals during the assay can also alter behavior. Most assays require that the animals be treated as gently as possible. Transfer by mouth pipette seems to be the most gentle although this in not recommended as a general lab practice. Gently moving animals with a pick is sufficient for most assays. If an individual animal is damaged in transfer and unable to move properly, then it usually is excluded from the data set. But, the rules for exclusion and the number of animals excluded should be reported.

### 1.6. Scoring behavior

To avoid ambiguity and inconsistency, it is critical to precisely define the criteria for scoring behavior both in the laboratory and in publications. For example, initiating backward locomotion is generally called a reversal. But, some researchers define a minimum distance the animal has to move backward to score as a bona fide reversal some do not. Some researchers include omega turns as reversals. And, some researchers count increased backward locomotion as a reversal or response most do not. A precise definition of the behavior to be scored is critical for analysis.

It is useful to have a “scoring worksheet” to record results for each behavioral assay. In addition to the actual scoring data, the ambient conditions, date, time, genotype, cultivation conditions, researcher name, number of animals scored, and other variables should be recorded.

### 1.7. Statistical analysis and reporting results

The number of animals assayed is determined by the assay. As a general rule, 4 large-scale population based assays or 30 individual assays with corresponding controls should be considered a bare minimum. To achieve statistical significance, many more trials may be required.

Data from experimental strains should always be compared to data from control strains analyzed in parallel.

Statistical analysis is critical for drawing conclusions from behavioral data. At a minimum, n and p values should be presented for critical data. Additionally, standard errors of the mean or standard errors should be presented within figures and tables to allow readers to assess significance.

Reproducibility can be difficult for behavioral assays. Control strains may vary in their response from day to day. Statistically, it may be tempting to normalize the data to the control results each day to decrease variation in the reported results. Although this has been done in some cases in the literature, it is clearly more persuasive to present data that has not been normalized. If normalized data is presented, then the non-normalized data should be presented in the corresponding on-line Supplementary Information.

### 1.8. Confirming results

It is wise to confirm the phenotype of strains, sequence plasmids and carefully check other reagents upon arrival. To avoid ambiguity, order crucial strains of C. elegans from the C. elegans Genetics Center (CGC) when possible. When they arrive, freeze multiple copies for long-term storage. Most C. elegans laboratories that specialize in behavior have their own “horror stories” in which genetic drift due to continuous passaging or mislabeling have wasted months of effort. It is a wise idea to thaw an aliquot of any crucial control strains at least once a year (e.g., the wild type N2 strain). Some labs thaw bi-monthly.

Background mutations: In addition to the mutant allele, C. elegans strains often contain other changes in their DNA. Some of these are spontaneous and some are background mutations arise from the original mutagenesis. And, because backcrossing is most effective for unlinked genes, the remaining background mutations may be tightly linked to the mutant allele and gene of interest. Historically, one strategy to confirm that the gene under examination causes the phenotype of interest is to create a trans-heterozygote (examining the behavior of allele A/allele B). If the alleles do not complement in the trans-heterozygous animal, then the mutant phenotypes are likely due to alterations in the function of gene X. Multiple, independently derived alleles of the gene of interest should also be examined if they are available.

Transgenic rescue of a mutant phenotype is the best indication that the behavioral phenotype observed is due to altered function of the gene of interest. For example, cDNA rescue using a heat shock promoter and a transformation marker (described below) may restore normal function to mutant animals. This phenotypic rescue by the cDNA should be confirmed by examining the behavior of transgenic mutant animals that carry the transformation marker and the “empty” heat shock promoter construct. Alternatively, a genomic rescue construct can be used to restore normal behavior, but a mutant version of the genomic rescue construct should not restore behavior.

Integrated transgenic arrays are caused by insertion of exogenous DNA in the chromosome. Therefore the behavioral phenotype of strain carrying an integrated array can arise either from the chromosomal DNA break or from the transgenes on the integrated array. If the behavior of animals carrying the extrachromosomal array is the same as the integrated array, then the behavioral changes are due to the transgene itself.

### 1.9. Transgenic strains

Transgenic strains: Some markers for generating transgenic C. elegans are preferred for behavioral analysis. GFP or dsRed reporter constructs can be used as transgenesis markers although these usually require the use of a fluorescent dissection microscope for strain maintenance. Historically, transgenic rescue of an unrelated mutant phenotype has been broadly used. Commonly used markers include pha-1 , lin-15 , dpy-20 , or unc-119 . Injection of a dominant rol-6 transgene is frequently used for transgenesis C. elegans but the rolling phenotype induced by this transgene interferes with most behavioral assays.

It is important to determine if the transgenic marker used will interfere with the assessment of the behavioral phenotype. GFP or dsRed expression can have deleterious effects. pha-1 , lin-15 , dpy-20 , or unc-119 mutant alleles or even rescued transgenic animals are defective in some behavioral assays.

### 1.10. RNAi

RNAi knockdown of gene expression is a powerful approach to assess the role of specific genes in neuronal function and behavior. Several approaches can be used with varying efficacy to knockdown gene expression with double stranded RNA in C. elegans . The magnitude of the RNAi knockdown varies dramatically from gene to gene this is an important consideration in interpreting experiments.

Feeding C. elegans bacteria expressing dsRNA for the gene of interest works in some cases. The nervous system is relatively refractory to RNAi compared to some other tissues, but useful results may still be obtained. Mutant strains with increased sensitivity to RNAi are often used to increase efficacy of gene knockdown rrf-3 and eri-1 are commonly used. Of course the behavior of control animals raised on control bacterial feeding strains should be examined. For example, as control for a nose touch response RNAi experiment, a bacterial strain expressing the dsRNA corresponding to osm-10 could be fed to rrf-3 and rrf-3 glr-1 animals. osm-10 is expressed in the ASH neurons that are critical for nose touch response, but loss of osm-10 function does not perturb nose touch response. rrf-3 animals raised on osm-10 RNAi bacteria should robustly respond to nose touch rrf-3 glr-1 animals should not as glr-1 is required for nose touch response.

C. elegans promoters can also be used to express dsRNA in transgenic animals. Usually an inverted repeat of coding sequence from the targeted gene is used for expression of dsRNA, but co-expression of sense and antisense sequences from two separate plasmids can induce RNAi knockdown for some genes. Ubiquitous and inducible gene knockdown can be attempted using common heat shock vector promoters. Cell-specific knockdown is sometimes also possible as dsRNA and RNAi effects spread poorly (if at all) between neurons.

### 1.11. Summary

C. elegans behavioral assays encompass a wide range of behaviors and approaches. When combined with current molecular biological, electrophysiological and optical recording techniques, behavioral assays have been remarkably successful in assessing the contribution of genes and specific neurons to behavior. Generous researchers who specialize in each technique have contributed the following protocols. We hope that by providing a resource for the community, that behavioral studies in C. elegans will be made easier, more accessible and clearer for neuroscience researchers in general.

## September 21, 2016

For the last few weeks I've been designing, building and experimenting with new tools for exploring the local structure of dense microcircuit connectomes. I spent yesterday developing a few demos to show off what I've done so far. The following notes are sketchy, but I'm hoping that the plots, associated captions and the introductory presentation I made during the San Francisco Neuromancer Rendezvous will provide enough context to give you an idea of what I'm trying to build.

This log entry emphasizes topological invariants as microcircuit features. However, more-traditional, graph-theoretic methods for identifying functionally-relevant patterns of connectivity in terms of network motifs may work equally well or better. In the following, you may be well served by focusing primarily on the figures and their captions, since the intervening text consists primarily of notes to myself for expanding this entry to provide a more complete account of this project.

Revise and summarize earlier notes on using topological invariants to investigate the structural and functional properties of local regions of densely reconstructed microcircuits [ &hellip ] review reasons for turning to the FlyEM dataset from Janelia [ &hellip ] enumerate some of the main advantages of using the extensive FlyEM metadata provided by Janelia, and, in particular, the opportunity it affords for testing automated analysis algorithms to infer function from structure. [ &hellip ] &larr

Mention related research at Janelia on the Drosophila visual system including, on the structural side, the work leading up to the seven-column medulla dataset [248, 281, 254], and, on the functional side, calcium imaging work out of Michael Reiser's lab [248]. Provide some detail on the resources offered in the FlyEM dataset and the extensive supporting tools and metadata. Note how the cell-type annotations and skeleton data facilitated much of the work described in this log entry.

Mention Alexander Borst's research on the fly visual system [ &hellip ] Borst and Euler [26] [ &hellip ] possible relevance to the Reichardt-Hassenstein motion model which posits specific circuits including cell types that could be explained by or identified with topological properties [ &hellip ] there are some obvious reasons why this would be challenging to achieve [ &hellip ] thoughts about what constitutes localized computation [ &hellip ] review of interpretations of topological invariants in the context of annotating neural circuits [51, 60, 89, 233] [ &hellip ] &larr

## Reference Request: Human visual system takes in \$10^7\$ bits/sec at the periphery and compresses it down to 50 bits/sec deep inside - Biology

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## Chapter XIV. In Sickness and in Health.

383. Arrangement of the Sick-room. This room, if possible, should be on the quiet and sunny side of the house. Pure, fresh air, sunshine, and freedom from noise and odor are almost indispensable. A fireplace as a means of ventilation is invaluable. The bed should be so placed that the air may get to it on all sides and the nurse move easily around it. Screens should be placed, if necessary, so as to exclude superfluous light and draughts.

The sick-room should be kept free from all odors which affect the sick unpleasantly, as perfumery, highly scented soaps, and certain flowers. Remove all useless ornaments and articles likely to collect dust, as unnecessary pieces of furniture and heavy draperies. A clean floor, with a few rugs to deaden the footsteps, is much better than a woolen carpet. Rocking-chairs should be banished from the sick-room, as they are almost sure to disturb the sick.

A daily supply of fresh flowers tends to brighten the room. Keep the medicines close at hand, but all poisonous drugs should be kept carefully by themselves and ordinarily under lock and key. A small table should be placed at the bedside, and on it the bell, food tray, flowers and other small things which promote the comfort of the patient.

The nurse should not sleep with the patient. Sofas and couches are not commonly comfortable enough to secure needed rest. A cot bed is at once convenient and inexpensive, and can be readily folded and put out of sight in the daytime. It can also be used by the patient occasionally, especially during convalescence.

384. Ventilation of the Sick-room. Proper ventilation is most essential to the sick-room, but little provision is ordinarily made for so important a matter. It is seldom that one of the windows cannot be let down an inch or more at the top, a screen being arranged to avoid any draught on the patient. Remove all odors by ventilation and not by spraying perfumery, or burning pastilles, which merely conceal offensive odors without purifying the air. During cold weather and in certain diseases, the patient may be covered entirely with blankets and the windows opened wide for a few minutes.

Avoid ventilation by means of doors, for the stale air of the house, kitchen smells, and noises made by the occupants of the house, are apt to reach the sick-room. The entire air of the room should be changed at least two or three times a day, in addition to the introduction of a constant supply of fresh air in small quantities.

385. Hints for the Sick-room. Always strive to look cheerful and pleasant before the patient. Whatever may happen, do not appear to be annoyed, discouraged, or despondent. Do your best to keep up the courage of sick persons under all circumstances. In all things keep in constant mind the comfort and ease of the patient.

Do not worry the sick with unnecessary questions, idle talk, or silly gossip. It is cruel to whisper in the sick-room, for patients are always annoyed by it. They are usually suspicious that something is wrong and generally imagine that their condition has changed for the worse.

Symptoms of the disease should never be discussed before the patient, especially if he is thought to be asleep. He may be only dozing, and any such talk would then be gross cruelty. Loud talking must, of course, be avoided. The directions of the physician must be rigidly carried out in regard to visitors in the sick-room. This is always a matter of foremost importance, for an hour or even a night of needed sleep and rest may be lost from the untimely call of some thoughtless visitor. A competent nurse, who has good sense and tact, should be able to relieve the family of any embarrassment under such circumstances.

Do not ever allow a kerosene light with the flame turned down to remain in the sick-room. Use the lamp with the flame carefully shaded, or in an adjoining room, or better still, use a sperm candle for a night light.

Keep, so far as possible, the various bottles of medicine, spoons, glasses, and so on in an adjoining room, rather than to make a formidable array of them on a bureau or table near the sick-bed. A few simple things, as an orange, a tiny bouquet, one or two playthings, or even a pretty book, may well take their place.

The ideal bed is single, made of iron or brass, and provided with woven wire springs and a hair mattress. Feather-beds are always objectionable in the sick-room for many and obvious reasons. The proper making of a sick-bed, with the forethought and skill demanded in certain diseases, is of great importance and an art learned only after long experience. The same principle obtains in all that concerns the lifting and the moving of the sick.

Sick people take great comfort in the use of fresh linen and fresh pillows. Two sets should be used, letting one be aired while the other is in use. In making changes the fresh linen should be thoroughly aired and warmed and everything in readiness before the patient is disturbed.

386. Rules for Sick-room. Do not deceive sick people. Tell what is proper or safe to be told, promptly and plainly. If a physician is employed, carry out his orders to the very letter, as long as he visits you. Make on a slip of paper a note of his directions. Make a brief record of exactly what to do, the precise time of giving medicines, etc. This should always be done in serious cases, and by night watchers. Then there is no guesswork. You have the record before you for easy reference. All such things are valuable helps to the doctor.

Whatever must be said in the sick-room, say it openly and aloud. How often a sudden turn in bed, or a quick glance of inquiry, shows that whispering is doing harm! If the patient is in his right mind, answer his questions plainly and squarely. It may not be best to tell all the truth, but nothing is gained in trying to avoid a straightforward reply.

Noises that are liable to disturb the patient, in other parts of the house than the sick-room, should be avoided. Sounds of a startling character, especially those not easily explained, as the rattling or slamming of distant blinds and doors, are always irritating to the sick.

Always attract the attention of a patient before addressing him, otherwise he may be startled and a nervous spell be induced. The same hint applies equally to leaning or sitting upon the sick-bed, or running against furniture in moving about the sick-room.

387. Rest of Mind and Body. The great importance of rest for the sick is not so generally recognized as its value warrants. If it is worry and not work that breaks down the mental and physical health of the well, how much more important is it that the minds and bodies of the sick should be kept at rest, free from worry and excitement! Hence the skilled nurse does her best to aid in restoring the sick to a condition of health by securing for her patient complete rest both of mind and body. To this end, she skillfully removes all minor causes of alarm, irritation, or worry. There are numberless ways in which this may be done of which space does not allow even mention. Details apparently trifling, as noiseless shoes, quietness, wearing garments that do not rustle, use of small pillows of different sizes, and countless other small things that make up the refinement of modern nursing, play an important part in building up the impaired tissues of the sick.

388. Care of Infectious and Contagious Diseases. There are certain diseases which are known to be infectious and can be communicated from one person to another, either by direct contact, through the medium of the atmosphere, or otherwise.

Of the more prevalent infectious and contagious diseases are scarlet fever, diphtheria, erysipelas, measles, and typhoid fever.

Considerations of health demand that a person suffering from any one of these diseases should be thoroughly isolated from all other members of the family. All that has been stated in regard to general nursing in previous sections of this chapter, applies, of course, to nursing infectious and contagious diseases. In addition to these certain special directions must be always kept in mind.

Upon the nurse, or the person having the immediate charge of the patient, rests the responsibility of preventing the spread of infectious diseases. The importance must be fully understood of carrying out in every detail the measures calculated to check the spread or compass the destruction of the germs of disease.

389. Hints on Nursing Infectious and Contagious Diseases. Strip the room of superfluous rugs, carpets, furniture, etc. Isolate two rooms, if possible, and have these, if convenient, at the top of the house. Tack sheets, wet in some proper disinfectant, to the outer frame of the sick-room door. Boil these sheets every third day. In case of diseases to which young folks are very susceptible, send the children away, if possible, to other houses where there are no children.

Most scrupulous care should be taken in regard to cleanliness and neatness in every detail. Old pieces of linen, cheese-cloth, paper napkins, should be used wherever convenient or necessary and then at once burnt. All soiled clothing that cannot well be burnt should be put to soak at once in disinfectants, and afterward boiled apart from the family wash. Dishes and all utensils should be kept scrupulously clean by frequent boiling. For the bed and person old and worn articles of clothing that can be destroyed should be worn so far as possible.

During convalescence, or when ready to leave isolation, the patient should be thoroughly bathed in water properly disinfected, the hair and nails especially being carefully treated.

Many details of the after treatment depend upon the special disease, as the rubbing of the body with carbolized vaseline after scarlet fever, the care of the eyes after measles, and other particulars of which space does not admit mention here.

### Poisons and Their Antidotes.

390. Poisons. A poison is a substance which, if taken into the system in sufficient amounts, will cause serious trouble or death. For convenience poisons may be divided into two classes, irritants and narcotics.

The effects of irritant poisons are evident immediately after being taken. They burn and corrode the skin or membrane or other parts with which they come in contact. There are burning pains in the mouth, throat, stomach, and abdomen, with nausea and vomiting. A certain amount of faintness and shock is also present.

With narcotic poisoning, the symptoms come on more slowly. After a time there is drowsiness, which gradually increases until there is a profound sleep or stupor, from which the patient can be aroused only with great difficulty. There are some substances which possess both the irritant and narcotic properties and in which the symptoms are of a mixed character.

391. Treatment of Poisoning. An antidote is a substance which will either combine with a poison to render it harmless, or which will have a directly opposite effect upon the body, thus neutralizing the effect of the poison. Hence in treatment of poisoning the first thing to do, if you know the special poison, is to give its antidote at once.

If the poison is unknown, and there is any delay in obtaining the antidote, the first thing to do is to remove the poison from the stomach. Therefore cause vomiting as quickly as possible. This may be done by an emetic given as follows: Stir a tablespoonful of mustard or of common salt in a glass of warm water and make the patient swallow the whole. It will usually be vomited in a few moments. If mustard or salt is not at hand, compel the patient to drink lukewarm water very freely until vomiting occurs.

Vomiting may be hastened by thrusting the forefinger down the throat. Two teaspoonfuls of the syrup of ipecac, or a heaping teaspoonful of powdered ipecac taken in a cup of warm water, make an efficient emetic, especially if followed with large amounts of warm water.

It is to be remembered that in some poisons, as certain acids and alkalies, no emetic should be given. Again, for certain poisons (except in case of arsenic) causing local irritation, but which also affect the system at large, no emetic should be given.

392. Reference Table of Common Poisons Prominent Symptoms Antidotes and Treatment. The common poisons with their leading symptoms, treatment, and antidotes, may be conveniently arranged for easy reference in the form of a table.

It is to be remembered, of course, that a complete mastery of the table of poisons, as set forth on the two following pages, is really a physician&rsquos business. At the same time, no one of fair education should neglect to learn a few of the essential things to do in accidental or intentional poisoning.