154 



THE AMERICAN MONTHLY 



[August, 



preciate the various possible sources 

 of error. Some confusion has arisen 

 in the assumption that the disease 

 kno^vn as i'07iget in France is the 

 same as the swine -plague of this 

 country. Some specimens of Pas- 

 teur's cultures of the Bacilhis of 

 rouget^ which is the same disease 

 as the rothlauf studied by Loffler 

 in Germany, were tested in the lab- 

 oratory, and it was found that the 

 diseases are quite distinct, and that 

 Pasteur's vaccine does not confer im- 

 munity against the swine-plague of 

 the United States. Pasteur's vaccine 

 contained a very minute Bacillus^ 

 which appears to be the same as 

 that already described by the Ger- 

 man investigators. 



Having thus disposed of the Ba- 

 cilhis of rouget^ by experiments in 

 cultivation and inoculation, it re- 

 mained still to discover the specific 

 microbe of the disease in qviestion. 

 It will be remembered that some 

 time ago Dr. Salmon announced the 

 discovery of a Micrococcus^ which 

 he then regarded as the cause of 

 swine-plague. Some successful in- 

 oculations were made with it, but 

 further opportunity for thoroughly 

 testing the matter did not present 

 itself. Last vear some well-defined 

 cases of the malady oftered the long- 

 desired opportunity to renew the in- 

 vestigations, and the results have 

 shown, in a most conclusive man- 

 ner, that the active agent in this 

 disease is not the previously de- 

 scribed Micrococcus^ but a species 

 of Bacterium. It is motile, of an 

 elongated oval form, usually seen in 

 pairs 1 . 3//-. — I . t//. in length by o. 6//. 

 in diameter. Its thermal death-point 

 is58°C. 



The reason for the previous fail- 

 ures to discover this organism is 

 principally the fact that it is very 

 difficult to isolate the specific mi- 

 crobe from the many others that are 

 found with it in the lesions of chronic 

 cases, such as had previously been 

 studied. In acute cases, which were 

 afterwards studied, the cultures were 



readily obtained pure. The best 

 soru'ce of the material for cultures is 

 the spleen. 



In the Annual Report of the De- 

 partment of Agriculture, i8Si-'82, 

 Dr. Salmon set forth a theory of im- 

 munity against contagiovis diseases 

 which has recently received consid- 

 erable attention. Some experiments 

 with the swine-plague bacterium have 

 lent confirmation to these views. The 

 theory is essentially as follows : 



The microbes of a disease are only 

 able to multiply within the animal 

 organism by virtue of a poisonous 

 principle produced by their gi'owth, 

 which acts upon the animal bioplasm 

 and modifies its activity, thus render- 

 ing it incapable of resisting the attack 

 of the germs. After a time, how- 

 ever, the tissues recover from con- 

 tinued action of the poison, and, 

 being no longer afiected by it, do not 

 permit the microbes again to gain a 

 foothold. Thus a single attack con- 

 fers immunity against a second. 



It is well known that the opinion 

 prevails at the present time that all 

 germ diseases are caused by peculiar 

 poisonous compounds produced by the 

 growth of the microbes, supposed to 

 be chemically related to the alkaloids, 

 and known by the rather inexpressive 

 name of ptomaines. Experiments 

 have clearly shown that the culture- 

 fluid of the swine-plague Bacterium., 

 after exposure to a temperature of 

 58° C. until completely sterilized, 

 when injected into pigeons renders 

 those animals proof against subse- 

 quent inoculation with the living 

 bacteria. Herein is one of the strong- 

 est experimental confirmations of the 

 theory of Dr. Salmon, and it may 

 lead to results of the utmost impor- 

 tance in the prevention and treat- 

 ment of disease. 



Among the various other microbes 

 found in swine-plague a peculiar chro- 

 mogene species has been studied and 

 is fully described in this report under 

 the name of Bacillus luteus {suis) . 

 It is a species possessing a most re- 

 markable tinctorial power, but for a 



