xo Obituary Notices of Fellows deceased. 
cannot be artificially produced in any of the laboratory animals. Inci- 
dentally, whilst in Egypt, he discovered amoebe in dysentery, and the 
bacillus responsible for the widespread ophthalmia in that country. 
As previously mentioned, at the time Koch was ordered to Egypt to 
investigate cholera, he was engaged in the attempt to discover some means 
to modify the infection by the tubercle bacillus in the animal body. 
Proceeding on the assumption that the tubercle bacillus exercises its patho- 
genic effects by means of a chemical poison, Koch investigated the action 
of the dead bacilli and their products upon normal animals, and also the 
effect of a previous injection with dead bacilli, upon a subsequent 
inoculation of living ones. This led to the important observation that in 
animals previously treated with dead bacilli, the later inoculation of living 
organisms occasioned an energetic local reaction, leading in some cases to 
their destruction. 
From his experiments he was led to the conclusion that, not only could a 
guinea-pig be immunised against tubercle by repeated injections of the 
products of tubercle bacillus, but that the same tissue reaction could be 
stimulated, and the disease brought to a standstill, by this means. Later 
(1890), he published his well-known results upon tuberculin, by means of 
which tuberculosis could be not only diagnosed, but in the early stages 
might, he hoped, be cured. The possible remedy was enthusiastically 
welcomed by the whole world. Medical men thronged to Berlin from all 
parts to see the results of its application. The treatment was applied to all 
sorts of cases in what we now know were colossal doses. The results were — 
disappointing, and in many cases disastrous. The premature publication of 
his results with tuberculin was a misfortune, and the failure of the treat- 
ment obscured for the time being the great value of Koch’s work, and even 
exposed him to opprobrium. _ Koch had, however, made a great discovery, 
but underestimated the potency of the agent he had brought to light. 
Tuberculin is an invaluable diagnostic for early tuberculosis in man and 
animals, and is universally employed. Since 1890 it has been consistently 
employed by a number of physicians all over the world for the treatment of 
tubercle with what appear to be beneficial results, and of recent years its 
employment has again been resuscitated by Wright. It is now administered 
in much smaller doses, and with careful observance of the effect of each 
injection. | } 
During the next eight years, 1891-1899, Koch was occupied with 
investigations into a large number of diseases of men and animals. The list 
includes leprosy, rinderpest, plague, surra, Texas fever, and malaria. These 
investigations necessitated his spending much of his time abroad. It would 
be difficult to adjudge just how much of the knowledge gained upon these 
diseases to attribute to Koch, as he was accompanied by one or more 
distinguished workers, as in the case of the German Plague Commission 
which visited India. It is very clear, however, from the published reports 
and papers, that the insight and experience with which he directed the 
