PLAGUE. 205 



phenomenon is exhibited among the pathogenic micro- 

 organisms only by the bacilli of chicken-cholera. These, 

 however, are larger than the plague-bacilli, and are of 

 absolutely no significance with relation to human beings. If 

 suppuration has not yet taken place, the diagnosis is not so 

 simple, although it appears most necessary just under these 

 conditions. Puncture of the buboes for this purpose was 

 considered by the Commission in its first communication 

 as not unattended with danger on account of the possibility 

 of opening a blood-vessel. It has, however, since been 

 shown that English physicians in plague-hospitals made 

 long incisions into the diseased glands, with subsequent 

 antiseptic treatment, for therapeutic purposes. In connec- 

 tion with this procedure fluid from the gland is readily 

 obtained for the purpose of making cover-slip preparations, 

 plates, and cultures. 



Microscopic examination of the blood yields successful 

 results only in cases of general infection. Cultural investi- 

 gation of the blood, however, yields better results. In 

 order to cultivate plague-bacilli from sputum, and, in general, 

 from bacterial mixtures, it is best to make gelatin streak- 

 cultures. The suspected material is spread in several 

 streaks upon the surface of a solidified gelatin-plate. The 

 plague-bacilli grow well at a temperature as low as from 

 22 C. (71.6 F.) to 25 C. (77 F.) ; while the associated 

 bacteria the diplococcus lanceolatus and the streptococcus 

 grow but feebly if at all. From a diagnostic point of 

 view it is further of the greatest significance that the blood- 

 serum of human beings and of animals that have recovered 

 from infection with plague possesses agglutinating activity 

 (German Commission). It is said that the serum does not 

 cause agglutination before the second week, and that this 

 is most marked in the second and third weeks. 



In cases of mixed infection, which occur especially in 

 conjunction with suppuration of the buboes, streptococci 

 appear, not only in the glands, but also in the blood. 



The prophylaxis of plague consists in disinfection 

 of all products of the disease that contain the specific 

 bacillus. In the first place, general hygienic precautions 

 should be observed, with especial regard to cleanliness and 

 ventilation of dwellings, care of the skin, etc. In general, 

 plague attacks preferably the lower classes of society, ex- 

 posed to want, filth, and misery. Isolation of plague- 



