Sept. 7, 1888.] 



SCIENTIFIC NEWS. 



243 



atmosphere. It is difficult to believe that the simple facts which 

 are all we know about it constitute its entire life history. It is 

 probably a transitory stage of some more complicated organism. 



I can only briefly refer to putrefaction. This is a far more com- 

 plex process than that which I have traced in the case of alcoholic 

 fermentation. In that nitrogen is absent, while it is an essential 

 ingredient in albuminoids, which are the substances which under- 

 go putrefactive changes. But the 'general principles are the 

 same. Here, too, we owe to Schwann the demonstration of the 

 fact that the effective agents in the process are living organisms. 

 If we put into a flask a putrescible liquid such as broth, boil it 

 for some time, and during the process of boiling plug the mouth 

 with some cotton wool, we know that the broth will remain long 

 unchanged, while if we remove the wool putrescence soon begins. 

 Tyndall has shown that if we conduct the experiment on one of 

 the high glaciers of the Alps the cotton wool may be dispensed 

 with. We may infer, then, that the germs of the organisms which 

 produce putrefaction are abundant in the lower levels of the atmo- 

 sphere, and are absent from the higher. They are wafted about by 

 currents of air ; but they are not imponderable, and in still air 

 they gradually subside. Dr. Lodge has shown that air is rapidly 

 cleared of suspended dust by an electric discharge, and this, no 

 doubt, affords a simple explanation of the popular belief that 

 thunderous weather is favourable to putrefactive changes. 



Cohn believes that putrefaction is due to an organism called 

 Bacterium termo, which plays in it the same part that yeast does 

 in fermentation. This is probably too simple a statement, but 

 the general phenomena are nevertheless similar. There is the 

 same breaking down of complex into simpler molecules ; the same 

 evolution of gas, especially carbon dioxide ; the same rise of tem- 

 perature. The more or less stable products of the process are in- 

 finitely more varied, and it is difficult, if not impossible, to say, in 

 the present state of our knowledge, whether in most cases they are 

 the direct outcome of the putrefactive process or residual products 

 of the protoplasmic activity of the organisms which induce it. 

 Perhaps, on the analogy of the higher plants, in which some of 

 them also occur, we may attribute to the latter category certain 

 bodies closely resembling vegetable alkaloids ; these are called 

 ptomains, and are extremely poisonous. Besides such bodies, 

 Bacteria undoubtedly generate true ferments and peculiar colouring 

 matters. But there is in most cases of putrefaction a profusion 

 of other substances, which represent the various stages of the 

 breaking up of the complex proteid molecule, and are often them- 

 selves the outcome of subsidiary fermentations. 



These results are of great interest from a scientific point of view. 

 But their importance at the present moment in the study of cer- 

 tain kinds of disease can hardly be exaggerated. I have already 

 mentioned Henle as having first found the true clue to animal 

 histology in the structure of plants. As early as 1840 the same 

 observer indicated the argument for regarding contagious diseases 

 as due to living organisms. I will state his argument in the words 

 of De Bary, whose "Lectures on Bacteria," the last work which 

 we owe to his gifted hand, I can confidently recommend to y ou 

 as a luminous but critical discussion of a vast mass of difficult and 

 conflicting literature. 



It was, of course, clear that contagion must be due togtbe com- 

 munication of infectious particles or contagia. These contagia, 

 although at the time no one had seen them, Henle pointed out, 

 " have the power, possessed, as far as we know, by living creatures 

 only, of growing under favourable conditions, and of multiplying 

 at the expense of some other substance than their own, and there- 

 fore of assimilating that substance. " Henle enforced his view by 

 comparison with the theory of fermentation which had then been 

 promulgated by Schwann. But for many years his views found no 

 favour. Botanists, however, as in so many other cases, struck on 

 the right path, and from about the year 1850 steady progress, in 

 which De Bary himself took a leading part, was made in showing 

 that most of the diseases of plants are due to parasitic infection. 

 The reason of this success was obvious : the structure of plants 

 make them more accessible to research, and the invading parasites 

 are larger than animal contagia. On the animal side all real pro- 

 gress dates from about i860, when Pasteur, having established 

 Schwann's theory of fermentation on an impregnable basis, took up 

 Henle's theory of living contagia. 



The only risk now is that we may get on too fast. To put the 

 true theory of any one contagious disease on as firm a basis as that 

 of alcoholic fermentation is no easy matter to accomplish. But I 

 believe that this is, notwithstanding a flood of facile speculation 

 and imperfect research, slowly being done. 



There are two tracts in the body which are obviously accessible 

 to such minute organisms as bacteria, and favourable for their 

 development. These are the alimentary canal and the blood. In 

 case cf the former there is evidence that every one of us possesses 



quite a little flora of varied forms and species. They seem for the 

 most part, in health, to be comparatively innocuous ; indeed, it is 

 believed that they are ancillary to and aid digestion. But it is easy 

 to see that other kinds may be introduced, or those already present 

 may be called into abnormal activity, and fermentative processes 

 may be set up of a very inconvenient kind. These may result in 

 mere digestive disorder or in the production of some of those 

 poisonous derivatives of proteids of which I have spoken, the effect 

 of which upon the organism of the part may be most disastrous. 



The access of bacteria to the blood is a far more serious matter. 

 They produce phenomena the obvious analogy of which to fermen- 

 tative processes has led to the resulting diseases being called 

 zymotic. Take, for example, the disease known as "relapsing 

 fever." This is contagious. After a period of incubation violent 

 fever sets in, which lasts for something less than a week, is then 

 followed by a period of absence, to be again followed in succession 

 by one or more similar attacks, which ultimately cease. Now you 

 will observe that the analogy to a fermentative process is very close. 

 The period of incubation is the necessary interval between the 

 introduction of the germ and its vegetative multiplication in 

 sufficient numbers to appreciably, affect the total volume of the 

 blood. The rise in temperature and the limited duration of the 

 attack are equally, as we have seen, characteristic of fermentative 

 processes, while the bodily exhaustion which always follows fever is 

 the obvious result of the dissipation by the ferment organisms of nutri- 

 tive matter destined for the repair of tissue waste. During the presence 

 of this fever there is present in the blood an organism, Spirochete 

 Obermeieri, so named after its discoverer. This disappears when 

 the fever subsides. It is found that if other individuals are inocu- 

 lated with blood taken from patients during the fever attack the 

 disease is communicated, but that this is not the case if the inocu- 

 lation is made during the period of freedom. The evidence then 

 seems clear that this disease is due to a definite organism. The 

 interesting point, however, arises, why does the fever recur ? and 

 why eventually cease ? The analogy of fermentation leads to the 

 hypothesis that, as in the case of yeast, the products of its action 

 inhibit after a time the further activity of the Spirochete. The 

 inhibiting substance is, no doubt, eventually removed partially from 

 theblood by its normal processes of depuration, and the surviving 

 individuals of Spirochete can then continue their activity, as in 

 lactic fermentation. With regard to the final cessation of the 

 disease, there are facts which may lead one to suppose that in this, 

 as in other cases, sufficient of the inhibiting substance ultimately 

 remains in the organism to protect it against any further outbreak of 

 activity on the part of the Spirochete, 



Here we have an example of a disease which, though having a 

 well-marked zymotic character, is comparatively harmless. In 

 anthrax, which is known to be due to Bacillus sublilis, we have 

 one which is, on the contrary, extremely fatal. I need not enter 

 into the details. It is sufficient to say that there is reason to believe 

 that the Bacillus produces, as one of those by-products of proto- 

 plasmic destruction to which I have already alluded, a most virulent 

 poison. But the remarkable thing is that this Bacillus, which can 

 be cultivated externally to the body, if kept at a heightened tem- 

 perature, can be attenuated in its virulence. It drops, in fact, the 

 excretion of the poison. It is then found that if injected into the 

 blood it does no mischief, and what is more extraordinary, if the 

 Bacillus in its most lethal form is subsequently introduced it too 

 has lost its power. The explanation of the immunity in this case 

 is entirely different to that which was suggested by a consideration 

 of the facts of relapsing fever. The researches of Metschnikoff 

 have led to the hypothesis that in the present case the white-blood 

 corpuscles destroy the Bacillus, When they first come into contact 

 with these in their virulent form they are unable to touch them. 

 But if they have been educated by first having presented to them 

 the attenuated form they find no difficulty in grappling with the 

 malignant. This is a very remarkable view. I should not have 

 put it before you had there not been solid reasons for regarding the 

 idea of the education of protoplasm with scientific respect. The 

 Plasmodia of the myxomycetes, which consist of naked protoplasm, 

 are known to become habituated to food which they at first reject, 

 and the researches of Beyerinck on the disease known as " gum- 

 ming " in plants have apparently shown that healthy cells may be 

 taught, as it were, to produce a ferment which otherwise they would 

 not excrete. 



If Metschnikoff's theory be true we have a rational explanation 

 of vaccination and of preventive inoculation generally. It is 

 probably, however, not the only explanation. And the theory of the 

 inhibitive action upon itself of the products of the ferment-organism's 

 own activity is still being made the basis of experiment. In fact, 

 the most recent results point to the possibility of obtaining protection 

 by injecting into the blood substances artificially obtained, entirely 

 independent of the organisms whose development they inhibit. 



