40 



expresses. The cultures are all highly virulent and retain their 

 virulence under artificial cultivation. 



The value of inoculation by the cutaneous method to demonstrate 

 the presence of plague infection in putrefying tissue is well known. 

 We have had one example in which the value of inoculation by this 

 method was proven in the case of a rat that was so badly decomposed 

 as not to admit of any opinion being formed as to whether the animal 

 was infected or not. A rat was brought from a warehouse where a 

 typical plague rat had been taken a few days previously. The 

 specimen was so badly decomposed that the abdominal organs could 

 not be distinguished with any degree of certainty. Smears from 

 tissue that was thought to represent spleen were negative so far as 

 pest-like organisms were concerned. A guinea pig vaccinated from 

 this splenic material died in seven days of typical plague, and a pure 

 culture of B. pestis was obtained from its organs. 



KoUe and Martini (9) compare the cutaneous method of inocula- 

 tion to the use of an agar plate in separating plague bacilli from 

 other organisms, and so regularly does B. pestis penetrate the skia 

 and infect the animal, and so rarely do other organisms do this, that 

 it offers a certain and accurate method of "filtering out" B. pestis 

 from any badly decomposed tissue. 



The technique of the cutaneous method of inoculation, or "vac- 

 cination" as it is sometimes called, is very simple. An area about 

 an inch square is shaven on an animal 's belly, taking care to abrade 

 the epithelium slightly. The culture or suspected tissue is rubbed 

 on this shaven area with a platinum loop or a dressing forceps. 

 Guinea pigs when inoculated in this manner generally die before the 

 seventh day; white rats die a day or two earlier. 



Kister (10) uses a drop of juice from an organ rich ia bacilli for 

 agglutination experiments with antipest serum. This would appear 

 in many cases to be of very material assistance, and the objection 

 that it is difficult to form a uniform emulsion of the bacteria would 

 be avoided. The well-known tendency of B. pestis to grow ia clumps 

 in culture is the main reason why agglutination reactions have not 

 been more extensively used in plague work. 



Skschivan (1) makes use of Pfeiffer's phenomenon in establishing 

 the identity of a given organism as B. pestis. 



To assist in the early diagnosis of plague, Dunbar and Kister (8) 

 practiced intraperitoneal inoculation of laboratory animals and 

 used a parallel series of immunized animals. As is well known, intra- 

 peritoneal inoculation with plague cultures or infected material leads 

 to the early death of the inoculated animal, and it is evident that 

 the survival of the immunized animal would afford considerable 

 evidence that the material used for inoculation contains B. pestis. 



