Ill. Food
D. Dangers to health from external influences
II. Infectious diseases
fever, dysentery and malaria are either exclusively or to a very large extent confined to tropical regions. Enteric fever and diarrhrea in children are observed more frequently in hot seasons than at other times. Many diseases peculiar to foreign countries run a comparatively mild course with the natives, while they are more serious for strangers, travelling through the country, who have not become acclimatized or accustomed to the new climatic conditions. Anyone, who, when changing climate does not adopt diligently a regular mode of life, or omits to adapt himself to the changed con-ditions according to the advice of experienced and intelligent persons, renders his body susceptible to such diseases, just as on the other hand, he, who in irrational exaggerated zeal suddenly changes completely the habits, necessary for his well-being also becomes an easy victim to disease germs.
176 D. Dangers to health from external influences.
infectious diseases we have to consider with regard to its propagation the direct communication or transfer as well as the indirect communication.
§ 188. Disease germs. For a number of infectious dis-eases we have succeded in obtaining the disease germs in the form of certain minute micro-organisms, already referred to repeatedly. In each of these diseases organisms, peculiar to each were found in the blood, the tissue, the juices and the excreta of the body; and these organisms were invariably absent in the case of healthy or differently affected persons.
We have succeded in rearing some of these germs on arti-ficially prepared feeding grounds, e. g. meat-broth, thickened by the addition of gelatine, and by transferring these arti-ficially bred germs to animals, have been able to produce in the latter the symptoms, peculiar to the disease in question.
Sometimes by accident, imprudence or experiments, which courageous savants have made on themselves, it has been proved that artificially-bred germs produce sickness in men.
These advances, made by science in the knowledge of disease date only from the last few years and are due in the first line to R. Koch j Thus is has been shown, how important a thorough investigation of the vital conditions of these micro-organisms is in order to understand and to overcome infectious diseases.
The majority of the living organisms, hitherto described as disease germs, are of' a vegetable nature and belong to the family of the fissi-parous fungi. Since many of them possess the form of short rods, they are called "bactel'ia" from the greek word for roll. They appear some-times singly, somesome-times in groups, or arranged in the form of a chain.
According to shape they are either rod-like (bacilli) or spherical (cocci);
some have a crooked form (comma-bacilli or vibriones); others the form of a screw or a worm (spirilli); many kinds possess more or Jess active movements of their own, others are motionless. The propagation of bac-teria is affected by fission; the young organisms, thus produced grow to the size of the parent bacteria and then in their turn divide themselves.
This process is repeated so rapidly, that milliards of micro-organisms may be produced within a few hours from a small number. Many kinds form
"spores", permanent structures, as within the individual spore a spheri-cal or egg-shaped body is formed, which is pre~erved in the fission of the original parent organism and is able to offer greater resistance to the effect of heat and cold and also to many substances, fatal to bacteria.
If a spore of this kind, which is somewhat similar to the seed of a plant is brought under conditions, favourable to its vitality, it grows to the size of the parent bacterium. Disease germs, which otherwise can thrive only inside the body may therefore retain their capacity development
outside the body in the shape of spores, and may reproduce themselves as soon as they penetrate into another body. All bacteria are so small, that they can be recognized only, when greatly magnified, and nearly all are particularly colourless; they are destinguished however in great part by the fact, that they can absorb and tenaciously retain certain colouring substances. Therefore, if a fragment of animal tissue, coagulated blood, etc. is treated with such a colouring substance and then washed, the teria alone remain coloured in the colourless tissue. In this way the bac-teria can be more easily recognised under the microscope than in their natural condition
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Fig. 42. Diagrammatic representation of Bacteria. (Greatly magnified.) 1. Cocci in chain form. 2. Cocci in groups. 3. Bacilli in a capillary vessel. 4 .
Comma-bacilli. 5. Bacilli with spores. 6. Very fine b1cilli.
The bacteria multiply in certain liquids to such a degree, that they are visible to the naked eye as a cloudy discoloration. On a solid sub-stance, on which they grow they form by their growth colonies, each con-sisting of millions of single organisms, but which appear to the unaided eye merely as minute drops, knobs, or slight protuberances. If, for in-stance a boiled potatoe is cut in two and exposed for some minutes to the air, and then placed under a glass shade, such colonies of bacteria may be observed on the cut surface after twenty four hours which have been developed from single bacteria deposited by the atmosphere.
By their growth the bacteria alter the composition of the feeding ground, as they withdraw from it certain substances, necessary for their structure and thus various chemical combinations may arise. In this way they cause many processes of fermentation and decomposition by action, similar to the yeast fungi, already mentioned. lVlany species of bacteria
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178 D. Dangers to health from external influences.
also separate poisonous substances from their feeding ground (§ 61) which may have even in very small quantities fatal effects on the human body;
other bacteria contain poison themselves. Thus by the nature and vital functions of the bacteria is explained the injurious effect on the human system peculiar to many of them. The illnesses, produced by bacteria originate, according to our present information either in the destruction of the tissues serving as their feedi11g ground or in the poisonous sub-stances separated by them or in their own poisonous action. Some in-fectious diseases are ascribed to activity of certain animal micro-organisms (Fig. 42).
Among the incalculably great number of bacilli only relatively few species are however injurious to health. The human body contains permanently inumerable small living organisms, which are partly harmless spores and partly assist in certain bodily functions e. g. digestion. Other germs are unable to exist inside the human body and perish as soon as they are introduced with food or otherwise. Lastly; there are also micro-organisms, which are not properly disease pro-ducers, but which may be injurious to health, if they pass into the body in large quantities, or have acquired abnormal qualities; among these are included some germs of decom-position and many bacteria, present even in the healthy intestines.
§ 189. Preliminary conditions of infection. The disease germs require certain predisposing conditions in order to be capable to produce their peculiar effects. The frequent ap-pearance of infectious diseases in certain places (endemics) or the sudden rapid spreading of such diseases (epidemics) their subsequent extinction and the immunity of other districts cannot be exclusively explained by the presence, absence or introduction of the corresponding micro-organisms. The nu-merous special circumstances, not yet completely investigated, which promote in endemics or epidemics the spread of disease germs 1 t at certain times, 2d in certain places and 3d among certain persons or classes of persons are provisionally described as 1 t temporal, 2d local and 3d personal "predispositions".
A temporal predisposition is afforded by the action of the weather, such as abnormal heat, moisture of the atmosphere, which temporarily provides conditions favourable to the spread and virulence of the disease germs. Many epidemics find a local predisposition among others in the neighbourhood of swamps in unhealthy or overcrowded dwellings, in a bad water-supply and in defective arrangements for the removal of refuse.
The importance of personal or individual "predisposition"
is very great. It is observed in times of epidemics, that only a limited portion of the population, exposed to the danger of infection, suffer; and some families are unusually susceptible to certain diseases of an infectious nature. The predisposition to many illnesses - e. g. consumption - is transmitted from the parents to the children and to the grand-children. Although in getting or not getting these infectious diseases chance in-fection plays a great part, and though the immunity of certain persons such as physicians during epidemics can easily be explained by their taking proper precaution, still we must assume an immunity in many men and a predisposition in others towards infectious diseases. The immunity from an infectious disease can be innate or acquired, but may be lost again under certain conditions, for instance in consequence of hardship or want of nourishment. It is known, that most people, after recovering from an infectious disease, for in-stance small-pox or measles are not attacked a second time by the same disease.
Recently it bas been found, that the inoculation of the
"serum" of the blood of animals, which have suffered certain infectious diseases, or which by certain methods of treatment have become immune to certain forms of illness, gives other animals or men the power of withstanding those diseases and sometimes indeed of becoming cured, when already infected with the disease. Efforts are being made at present to realize these observations for combating infectious diseases (cf. § 206).
§ 190. Preventive measures against infectious diseases.
The efforts towards warding off infectious diseases had already led to good results before the germs of disease in the micro-organisms had become know. In former times epidemics wrougth far greater devastation than at present. In the four-teenth century the black death is reported to have carried off 25 millions of people i. e. about the fourth part of all people then living in Europe. Small-pox and typhus alone caused regularly more deaths than all infectious diseases at present.
Especially the number of cases of infectious diseases dimi-nished considerably, where attention was paid to the rules of hygiene.
In the Prussian army in 1869 22 216 soldiers were attack-ed by infectious diseases; after ten years the number fell to
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180 D. Dangers to health from external influences.
11467; ten years further the number of cases was only 4695;
and in 1895 only 4077 soldiers were attacked by infectious disease; although the numerical strength of the Prussian army has been considerably increased since 1870.
Munich was formerly considered as very unhealthy; for between 1850 and 1860 213, in 1858 as many as 334 and between 1867 and 1875 130 persons per 100000 of the in-habitants yearly died of typhoid fever. Upon the advice of von Pettenkofer it was decided to improve the sanitary con-ditions of the town. Care was taken to have a suitable re-moval of refuse; private slaughter-houses were abolished alto-gether and good drinking water was procured by obtaining spring water brought into town through an aquaeduct. Since then the number of cases of death diminished constantly;
already between 1876 and 1878 only 42 died on the average yearly and from 1893 to 1899 only 5 persons of 100000 die on an average yearly in Munich from typhoid fever. Similar results in respects to the decrease of infectious disease have been shown in many other German towns; such as Berlin and Dantzig in consequence of sanitary improvements.
As the power of resisting infection in the individual is increased by proper mode of life and suitable nourishment, so an efficacious means of combating infectious diseases is found in the healthy arrangemont of communities. Never-theless man is not sufficiently protected against infection without additional safeguards .
. § 191. Combating infectious diseases. In the chapter on commerce we have already described the means adopted for preventing the spread of infection from place to place and from country to country. In order to be able to suppress effectually an epidemic, that . has broken out in a town or country, it is necessary that every case of it should be prompt-ly reported to the authorities; furthermore each case should be supervised so as not to become the starting-point of further infection. The essential means for these purposes are: pt the duty imposed on doctors, the relatives of the sick, or other people responsible for them, of notifyiny the illness; 2d the iso-lation of the sick (and if necessary of persons having inter-course with him) from the healthy population; and 3d the de-struction or disinfection of the disease germs in the excreta of
the sick, in their linen and clothing and in all objects, to which the infectious matter might adhere.
For destroying disease germs the best means is burning;
but such an extreme measure is only resorted to, when dis-infection would be too costly in comparison to the value of the tainted object. A disinfecting process should be effec-tive, cheap, harmless to the objects treated by it and free from danger to the persons entrusted with its execution. Dis-infection is effective, if it destroys the infectious matter or
renders it innocuous, a goal, that can be attained only under the guidance of skilled persons.
The following processes are used for disinfection.
1. Heating by steam. For this process are used either movable, steam-producing apparatus which are brought from place to place like locomo-tives, or stationary boilers, erected in special disinfecting rooms. Steam apparatus, from which a reliable result is to be expected should be exa-mined by competent persons and attended to by trained workers. When well-constructed and properly-fed ones are used, the steaming process destroys disease-germs with great certainty and possesses the advantage of not injuring most objects. However, leather objects, furs, india rubber goods, glued, polished or veneered articles, some metal wares and many kinds of furniture are rendered valueless by it and hence should not be disinfected in this way. The finer articles of clothing require mending and pressing after the action of the steam. Cloth or linen garments, which have been defiled with blood, matter or human excreta should be washed before being placed in the steam apparatus, or otherwise permanent stains are usually left behind. All objects, disinfected by steam are benefited by being protected from the water deposited during cooling by means of coverings of sacking etc.
2. Boiling. The objects to be disinfected are placed in boiling water, to which some soda has been added. 'l'he process is easily carried out, and when continued long enoug·h produces reliable results; it is how-ever inapplicable to many objects. It is most suitable for underclothing, small metallic objects, utensils etc.
3. Chemical treatment. a) Solution of carbolic soap. To a solu-tion, consisting of 3 parts of soft-soap and 100 parts of water 5 parts of commercial carbolic acid are added, while the solution is being constantly stirred. Linen and other suitable material are steeped for a long time in the solution; wooden articles, floors, the walls of rooms, shoes and other leather articles are washed with it. Sometimes the soap solution without the carbolic acid is sufficient. The smell, caused by the acid is removed from the disinfected objects by washing or airing.
b) Whitewash. This is prepared by mixing one part of broken, well-burnt lime with 4 parts of water. It is best carried out in the following manner. In the preparing vessel only a small portion of the water is first poured; the lime is added, which absorbs the water and in a short time is retluced to powder, steam and heat being thereby
produ-182 D. Dangers to health from external influences.
ced. Then the rest of the water is added, while the contents are kept stirred. The disinfecting fluid, prepared in this way should be kept in well-closed vessels and be shaken before being used. In handling white-wash care should be taken that none of it is allowed to come in contact with the eyes, as it is a corrosive fluid, highly injurious to the eyes.
Whitewash is particularly suitable for disinfecting the excreta of the sick. When thoroughly mixed in equal proportions with the latter it kills the disease germs or micro-organisms therein in a short time. It is also used with advantage for disinfecting the sick-room by washing or painting the walls and floors admitting such treatment, and repeating the process after a short interval.
4. Beating, brushing, airing, sunning. This treatment is applied to objects, which would be rendered useless by boiling or wetting, as well as to objects, which would be unsuitable for disinfection by steam, e. g.
many upholstered articles. The process suffices for the removal of certain disease germs; it is not be relied on however.
5. Other means. Some other disinfecting processes are used, ac-cording to the circumstances of the case. Thus, a number of chemical substances, e. g. corrosive sublimate (a mercurial compound) formaldehyde, thymole, chloride of lime and of zinc are useful means of disinfection in certain cases. Some of them are specially suitecl for destroying diseased matter on the hands and other parts of the body, but in such cases a thorough soaplather with a brush should precede disinfection. The whole body is most thoroughly disinfected by a bath with plentiful use of soap.
Infectious substances are removed from wall paper by rubbing them with breadcrumbs, which should be burnt after being used; or the wallpaper is entirely removed, to that the walls may be whitewashed. The joinings of the boards in the floor should be sprinkled with the disinfecting fluids;
sometimes it is necessary to remove the entire dust from under the floor (cf. § 115).
Formaldehyde is a gaseous body, which is easily soluble in water, and is employed in aqueous solution as well as in the gaseous state.
Recently several methods have become known for the employment of gaseous formaldehyd for disinfection by all of which only the disease germs on easily attainable surfaces are killed with certainty; e. g-. on wallpaper (tapestry). Woven materials (cloaks, quilts), or porous objects are not pierced through by the gas. A disinfection with formaldehyde should be only undertaken with the advise of a physician and under his supervision.
Unfortunately, some unreliable modes of disinfection are still largely em-ployed. Among them are the treatment of the object with sulphate of iron or of copper, or with sulphuric acid. Even fumigating- with chlorine gas and spraying- with diluted carbolic acid are often insufficient, because the disinfectants are not used in sufficient quantities.
The manner, extent and duration of disinfection should in every case be decided by an expert preferably by the doctor, and the execution of the process should be placed under medical supervision, so far as it cannot be entrusted to special dis-infecting works. Establishments of this kind are to be found in many large towns and in many country districts. The