232 



STRONG AND TEAGUE. 



As another example of the importance of the portal of entry 

 of the organism in relation to infection and immunity may be 

 cited the fact that the tetanus bacillus, which frequently resides 

 normally as a harmless commensal in the intestine of the horse, 

 when injected beneath the skin of this animal, may produce 

 tetanus and death. 



These examples serve to emphasize the importance of experi- 

 mental work upon the subject of protective inoculation against 

 pneumonic-plague infection, and show that it does not follow 

 that, because there is evidence that protective inoculation is 

 sometimes successful in the case of bubonic plague, it will neces- 

 sarily also be efficient in the case of pneumonic plague. 



In our experiments in immunization, we used both guinea pigs 

 and monkeys. In selecting a method of prophylactic inoculation 

 for the production of the immunity, we naturally chose the one 

 of vaccination; that is, inoculation with a living attenuated or- 

 ganism, as this method unquestionably has been shown to produce 

 a much higher immunity against bubonic-plague infection than 

 any other in which killed cultures of the plague organism or its 

 extracts are employed. 



The accompanying Table I, taken from the previous experi- 

 ments of one of us (Strong) ,- shows the comparative value of the 

 different methods of immunization employed against cutaneous 

 and subcutaneous plague infection in animals. 



Table I. — Combined table comparing efficiency of different methods of 



immunization. 



KILLED PEST CULTURES. * 



Kind of animal and series No. 



Number 

 inoc- 

 ulated. 



Number 



dead 



before 



immunity 



tested. 



Immunized. 



Number. 



Percent- 

 age. 



Monkeys: 



Bouillon-cultures — 



8 

 9 



3 



20 

 15 





3 

 2 



37 

 22 



Series 49 . ._ . 





Agar-cultures — 



Series 9 - . 





Series 25 



3 

 1 



4 

 4 



23 

 28 



Series 48 



Total 



55 



4 



13 



25 



Guinea pigs (killed agar-cultures) : 

 Series 50 (total) 



15 





4 



26 







This Journal, Sec. B (1907), 2, 238. 



