110 



SCIENCE. 



[Vol. V., No. 105. 



tablish in a definite manner the specific patho- 

 genic power of a micro-organism, which, by its 

 presence in the blood, tissues, or alimentary 

 canal, may be supposed, a priori, to bear a 

 causal relation to the disease with which it is 

 associated. 



This proof depends upon the production of 

 characteristic morbid phenomena by inoculat- 

 ing susceptible animals with ' pure cultures ' of 

 the parasitic micro-organism previously found 

 under circumstances to justify^ the supposition 

 that it bears an etiological relation to the dis- 

 ease under investigation. This final proof 

 Koch has attempted to obtain with reference 

 to the so-called ' comma bacillus,' which, ac- 

 cording to his observations, is constantly 

 associated with epidemic cholera, and, after 

 numerous failures, claims finally to have suc- 

 ceeded. In a late number of the Deutsche 

 medicinische wochenschrift, he says, — 



" The experiments of Rietsch and Nicati have 

 been lately repeated at the Imperial board of health; 

 a pure cultivation being so far diluted, that the 

 amount injected contained scarcely a hundredth part 

 of a drop of the cultivation liquid. The liquid was 

 injected into the duodenum without previously bind- 

 ing the ductus choledochus. With few exceptions, 

 the animals so treated died within a space of time 

 extending from a day and a half to three days. The 

 mucous membrane of the small intestine was red- 

 dened: its contents were watery, colorless, or slightly 

 reddish tinged, and at the same time flaky. Comma 

 bacilli were found in the contents of the intestine 

 in a pure cultivation and in extraordinary numbers, 

 so that the same phenomena were visible here as 

 are seen in the cholera intestine in its fresh state. 

 Owing to the small quantity of infectious matter 

 used for injection, the idea of a simultaneous intoxi- 

 cation from poisonous matters contained in the culti- 

 vation liquid used for injection is excluded." x 



In face of the previously reported failures 

 to produce cholera in the lower animals,' we 

 are disposed to receive the proof now offered 

 with some reserve, inasmuch as the injections 

 seem to have been made through the walls of 

 the abdomen directly into the intestine. This 

 method has, no doubt, been adopted upon the 

 supposition that previous failures were due to 

 destruction of the bacilli by' the acid juices of 

 the stomach when they have been introduced 

 by the mouth. There is nothing improbable 

 in this supposition ; but, on the other hand, 

 the possibilit} T that when the material is in- 

 jected directly into the intestine the puncture 

 made may have been a serious complication 

 and source of error, at once suggests itself. 



That micro-organisms closely resembling the 

 ' comma bacillus ' are to be found in the healthy 



1 Quo'ed from the British medical journal of Nov. 22, 1884, 



human mouth, and in the discharges of patients 

 with other forms of intestinal flux, cannot be 

 doubted ; but that these are identical with the 

 ' comma bacillus ' cannot be established upon 

 morphological grounds alone. If one ' comma 

 bacillus ' in pure cultures produces cholera, 

 and another having identical morphological 

 characters does not, we must admit an essen- 

 tial difference — physiological — which, if con- 

 stant, must be considered a specific character, 

 equal in value to a constant difference in form 

 or in color. If such difference is not constant, 

 it will at least establish a pathogenic variety of 

 the ordinarily harmless organism. But this is 

 not the state of the question as regards Koch's 

 ' comma bacillus : ' for in his answer to Prof. T. 

 R. Lewis of the English army medical school, 

 who asserts that a curved bacillus, identical 

 with the ' comma bacillus,' is found in normal 

 human saliva ; and to Professors Finkler and 

 Prior, who claim to find similar organisms in 

 the discharges of patients with cholera nostras 

 (sporadic cholera) , — Dr. Koch shows very 

 conclusively' that the organisms referred to are 

 not identical with the ' comma bacillus,' al- 

 though bearing some resemblance to it. This 

 conclusion is based both upon appreciable mor- 

 phological differences, and upon the different 

 behavior of the organisms when cultivated upon 

 gelatine. 



Through the courtesy of Dr. Billings of the 

 army, I have recently had an opportunity to 

 study the morphology of the ' comma bacillus,' 

 having had in my possession for several days a 

 slide sent by Koch himself to the Army medical 

 museum. My laboratory assistant, Dr. A. 

 C. Abbott, has made for me a camera lucida 

 drawing, which, I think, fairly represents the 

 organism as seen in this slide, and which is 

 reproduced in fig. 1. Each separate ceil was 

 drawn under the camera lucida ; but the field as 

 a whole is an ideal one, as I desired to show in a 

 single figure all of the forms found in the slide. 

 As a matter of fact, the ' commas ' as seen at 

 a are by far the most numerous, and are found 

 clustered in groups and masses ; while the 

 characteristic spirilla, such as may be seen at 

 the centre of the field at i, are comparatively 

 scarce. Still, in view of the intermediate 

 forms, as seen at c, I cannot doubt that we 

 have here a pure culture of a single organism, 

 and that this organism is in truth a spirillum, 

 and not a bacillus. If one saw only such 

 forms as we have delineated at e, there would 

 be no hesitation in pronouncing them bacilli ; 

 and the name ' comma bacillus,' from a mor- 

 phological stand-point, applies very well to the 

 prevailing form, as seen at a. It is not sur- 



