478 INFECTION AND RESISTANCE 



sociated with the bacterial ectoplasm, which becomes active when the 

 bacteria enter the animal body, and a truly endocellular poison which 

 does not become active until the surrounding ectoplasm is dissolved. 

 They believe that sensitizing bacteria is a method for the production 

 of endotoxin, and think that therefore the ideal serum for the treat- 

 ment of typhoid consists of a mixture of two sera produced each 

 with one of the antigens, that is, with sensitized and unsensitized 

 bacteria. Rommel and Herman 73 did not obtain encouraging results 

 with this serum. 



From a study of the literature it seems to us that in spite of the 

 many different methods of production employed by various observers 

 in their studies on typhoid sera it is quite likely that all these sera 

 are essentially alike, containing, quantitatively, according to the de- 

 gree of immunization, bactericidal, agglutinating, and opsonic prop- 

 erties, with possibly a limited amount of neutralizing power for the 

 poisons liberated from the typhoid bacilli in the body. As far as we 

 can judge from clinical reports the therapeutic value of the sera 

 so far produced is not very great. It seems that cases treated early 

 in the disease may be benefited, and possibly an early cessation of 

 the bacteriemia can in this way be attained. However, it does not 

 seem either theoretically or from the study of clinical publications 

 that any very marked effects have followed the use of any of the sera 

 in advanced cases. 



THE SEKUM TREATMENT OF PLAGUE 



That the serum of animals immunized with killed plague cultures 

 may actively protect normal animals from experimental infection 

 was first shown by Yersin, Calmette, and Borrel. 74 The serum which 

 they produced possessed apparently powerful bactericidal action, 

 but no antitoxic properties were demonstrated. They determined 

 its protective powers by injecting measured quantities into mice and 

 infecting them with fatal doses of virulent plague bacilli 24 hours 

 later. The Yersin serum which was produced for the treatment of 

 plague as a result of these experiments was made, then, by the 

 gradual immunization of horses with first dead plague bacilli, finally 

 with virulent living organisms. The serum has been extensively 

 used by many observers with results that leave one much in doubt 

 as to its efficacy. Yersin 75 himself, reporting on an epidemic in 

 IS^hatrang, reports a general mortality of 73 per cent, for the whole 

 epidemic, a mortality of 100 per cent, in untreated cases, and of 42 

 per cent, among those treated with his serum. Good results were 

 also reported from the epidemics in Amoy and Canton in 1896.. 



73 Rommel and Herman. Centralbl. f. Bakt. Ref . Vol. 53, 1912. 



74 Yersin, Calmette, and Borrel. Ann. de I'Inst. Past., 1895. 



75 Yersin. Ann. de I'Inst. Past., 1899. 



