Emil von Behring

“ Although the number of persons dying of consumption is frightfully large, the number of tubercular, and tubercularly infected, persons is much larger. Not until recent years have we secured tolerably reliable data to enable us to judge of the distribution of tuberculosis in civilized countries.
If we classify as tuberculous every case in which there are pathological changes due to tubercle bacilli, then surely the oft-quoted saying of the noted Greifswald physician is true, “We are all a bit tuberculous.” ”

“ If a coughing consumptive lives together with a new-born child, especially if cleanliness leaves much to be desired, it is impossible for this child to avoid infection with tubercle bacilli. They are present in the particles of sputum which are scattered about everywhere, and they thus gain access to the mouth and nose of the infant. From there they reach the intestinal mucous membrane, which they penetrate, and so they invade the body juices. Not alone infants, but older persons as well, are endangered in the home of the consumptive. ”

“ I have quoted the statistics of the high infant mortality in our large cities merely in order to advance a further epidemiological argument for my assertion that the infant alimentary tract is defenseless against infectious agents whether these [Pg 39] are living or not. Even the infectious toxins pass unchanged through the intestinal mucous membrane of very young individuals, though not through that of healthy older ones. A real advance in milk hygiene can, however, be begun even now if the milk be pasteurized at the dairies and not at the large receiving-stations in the cities. ”

“ Under the last I understand all the conditions necessary to bring the virus to such a part of the living organism as will enable it to enter either into the circulation or into other body juices.
Every human individual is by nature susceptible to the action of tubercle bacilli which have entered his body juices. This is true not only of human but also of bovine tubercle bacilli. I emphasize this now but shall give my proofs later. But not every tubercular infection of the tissues leads to consumption. ”

“ The suppression of tuberculosis is of universal interest. A disease which is so wide-spread and which attacks the human race from so many points can be successfully combated only by the cooperation of many different agencies. It is therefore of great importance that the origin of tuberculosis be well understood not only by physicians, but by many outside the medical profession, such as dairy- and cattle-men, officers of health boards, sanitary engineers, etc. ”

“ It is unnecessary for me to further emphasize the necessity, in infant feeding, to insist under all circumstances on milk absolutely free from tubercle bacilli; nor, what is equally obvious, that it is absolutely necessary to keep coughing consumptives away from infants. But I should like to observe that not only infants but also older persons should be protected against the possibility of infection, if we have any reason to fear that the [Pg 43] alimentary tract is anywhere deficient in its protective epithelial covering. ”

“ Nowadays the term tuberculosis is applied to everything which constitutes a change in the organism excited by the entrance into it of tubercle bacilli. In statistics, galloping consumption is thus classed with tubercular local infection of a joint, gland, abdominal organ, of a little nodule in the skin of the face, etc. Calcified as well as other remains of previous lesions are classed as tubercular. [Pg 4] We have every reason to praise as a great scientific advance the discovery that in manifestations so varied in their importance to life and health the etiological factor is the same. ”

“ In the same sense we must regard the temporary residence of tuberculous individuals in sanitaria as most valuable, for even if the lesions do not heal there, the progressive downward course of the disease is checked and the patients learn for the rest of their lives to appreciate what will benefit and what will harm them. In many cases, therefore, these sanitaria will prove themselves homes for the prevention of consumption, even if they are not homes for the cure of tuberculosis. ”

“ Nowadays all botanists and zoologists are agreed on this, that membership in a species is determined by the origin of the organism. An anthrax culture, which has been made entirely avirulent by means of Pasteur’s procedure for reducing virulence, surely belongs to the same species as does the virulent variety from which it was derived. And in this [Pg 16] case the difference in the degree of virulence is far greater than it ever is between human and bovine tubercle bacilli. ”

“ If we allow an individual, entirely free from tuberculosis, to breathe tubercle bacilli, the opportunity for an intestinal [4] infection is surely [Pg 29] presented; on the other hand, that any bacilli whatever reach the lungs directly cannot be positively affirmed. Infection of the organs of the pharynx and larynx in these cases always corresponds to disease of the lymph-vessels and glands in the neck, and gives the individual the scrofulous habitus. ”

“ One can maintain without exaggeration that tubercular lupus, tubercular scrofula, and other human tuberculosis localized in joints, serous surfaces, etc., are just as little identical with pulmonary consumption as are the cases of bovine perlsucht. The term identical does not even fit all cases of consumption. Strictly speaking, a process or thing is identical only with itself. Certainly not all tubercle bacilli are identical, nor yet all kinds of tubercle bacilli. ”

“ We need not, however, idly fold our hands and [Pg 25] become fatalists who see the inevitable destruction of the human race by tuberculosis. Tubercular infection does not by any means signify tubercular consumption. It is just this enormous diffusion of tubercular infection which demonstrates, better than anything else, the curability of many tubercular diseases, their liability to spontaneous cure; for I must admit that I have little faith in the curative action of any of the numerous methods of treating tuberculosis. ”

“ This assertion will at first sight be surprising, for it has long been maintained that the suckling infant receives milk free or almost free from germs. Mother’s or nurse’s milk is taken by the child in this condition, and the cow’s milk for artificially nourished children is usually first boiled or scalded. In later life, to be sure, much less attention is paid to securing a milk as sterile as possible. How, then, is this to be reconciled with the above statement, that it is especially the milk fed to infants which constitutes the chief danger in causing tuberculosis? ”

“ Pathological changes, accompanied by the shedding of epithelium, occur especially in the exanthemata, and particularly after measles. The laity has long noticed this close relation between measles and tuberculosis. In the infant, the disposition to intestinal tubercular infection is entirely physiological and normal. The healthiest and strongest infant is exposed fully as much as the weak, sickly one, and perhaps more so, for in the latter other parasites are contending for the cells on which they feed. ”

“ Nor does their state of nutrition, milk production, or calf-raising leave anything to be desired. Now and then a cow coughs, or, despite plentiful food, loses flesh. This animal is put aside and the herd, as such, resumes its magnificent appearance. If in a herd reacting to tuberculin things are allowed to go on in this way for a number of years, especially if the cattle be barn-fed, then, to be sure, the number of coughing animals increases, the offspring deteriorate, the milk and meat production decrease, until finally the scourge of tuberculosis is plainly marked. ”

“ For adults who, in healthy circumstances, possess a strong protection against the action of the tubercle bacilli, in the form of the epidermis, the epithelial covering of the mucous membranes, and the anti-bacterial ferments, I regard the danger of infection as not particularly great, provided, of course, the dose introduced is not as large as in our laboratory experiments. ”

“ If, by the time the milk reaches the city, the proliferation of these pathogenic micro-organisms has already gone on to a considerable extent, then usually the milk will contain a number of poisonous substances in addition to the micro-organisms. Some of these germs are killed by the scalding to which the milk is usually subjected before feeding, and the virulence of the rest is much diminished, so that in boiled milk practically no danger is to be apprehended from the micro-organisms. ”

“ The acute miliary tuberculosis in man, which can be clinically diagnosticated, is to be regarded as a provocative secondary infection, resulting from scrofula of the blood-vessels’ intima when, on the disintegration of cheesy intima tubercles, a great many tubercle bacilli are thrown into the circulation at once. ”

“ However, in the light of our present biological knowledge, based on Darwin’s theory of evolution, we are under no circumstances permitted to take as a criterion for like and unlike species such an easily influenced factor as the degree of virulence, i.e., the capacity for giving rise to pathological changes in another organism. ”

“ I have succeeded, especially in goats, but also in other [Pg 28] animals, in producing a clinical picture exactly similar to that of human pulmonary consumption. In these animals I first produced a moderate degree of immunity against tuberculosis by a lengthy course of treatment, and then I injected a strong tubercular virus into the circulation. I regard the lesions in pulmonary consumption as being produced in similar fashion. They are the expression of an infection in an individual who, owing to a very early previous infection with tubercle bacilli, is less susceptible to the new infection. ”

“ Whether adult persons in whom the conditions [Pg 50] are favorable for an intestinal infection with Tb. will develop primary tubercular lesions in the intestinal wall, or in the mesenteric glands and the peritoneum, will depend mainly on the circumstance whether or not, owing to a previous infection, they have become oversensitive to tuberculin. Individuals oversensitive to tuberculin are inclined to develop lesions at the point of entry of the tubercular virus, if opportunity is given for the introduction of the virus by means of leucocytic wandering cells. ”

“ Another important problem, one regarding hereditary immunity, is already nearer solution. I believe I am warranted in saying that, as a rule, the immunity against tuberculosis is not transmitted by the cow to her calf during intra-uterine life. One can readily be deceived by cases of apparent hereditary immunity. For example, in examining the fourteen-day-old calf of a highly immunized cow, I found the calf to possess a comparatively high degree of immunity against perlsucht bacilli. ”

“ Yet it is etiologically that the vital processes must be analyzed if we wish to have a firm basis for our struggle against preventable diseases. This has more and more become the opinion of modern physicians. The progress that has been made, first in surgery and then in internal medicine, progress that only fifty years ago was declared by the most eminent representatives of medicine in those days to be impossible, has been possible only through the etiological investigations developed by Pasteur and by Koch. ”

“ It may be months, years, or decades before the infection leads to manifest disease. This depends on the virulence of the virus, which is generally much greater in the virus of bovine tuberculosis than in that of human tuberculosis. It also depends on the number of bacilli introduced per stomach, and whether such introduction is single or oft repeated. In the human being months and years may elapse before the infection is followed by any sensitiveness to tuberculin injections in the usual dose. ”

“ It was but a step from this discovery to the assumption that the mucous membrane of infants might behave similarly toward bacteria. For my first experiments I selected anthrax bacilli, which, when free from spores and given in milk per stomach, do not affect adult guinea pigs at all. They are quite rapidly thrown off with the excreta, remaining, however, a little longer in the cæcum. When the same dose of bacilli was administered in this way to guinea-pigs less than eight days old, they died just as rapidly of anthrax as by the customary method of infection. ”