84 STUDY AND IDENTIFICATION OF BACTERIA. 



abdominal walls as they are turned back, fluid in the pleural cavities, 

 ccdematous haemorrhagic swelling of the neck glands, and in particu- 

 lar a creamy, mottled appearance of the liver. Smears from the spleen 

 will show the oval bacilli. 



Recent investigations in India have definitely determined the fact 

 that the flea (Pulex cheopis) is the intermediary in the transmission of 

 plague from rat to rat and from rat to man. In pneumonic plague the 

 infective nature is very great and appears to be by the respiratory 

 atrium. This was the terrifying type of plague in the black death of 

 the fourteenth centurv. 



FIG. 32. Pest bacillus involution forms produced by growing on 3% salt agar. 

 (Kolle and Wassermann.} 



For diagnosis make smears and cultures from material drawn from 

 a bubo by a syringe. (At a later stage, when softening begins, there 

 may not be any bacilli present.) Also, if pneumonic plague, from the 

 sputum. Blood cultures and even blood smears may be employed in 

 septicaemia plague. Formol fuchsin makes a satisfactory stain. 

 Always inoculate a guinea-pig with the material either by rubbing it in 

 with a glass spatula on the shaven skin or by subcutaneous injection. 

 For prophylaxis the most important method is that of Haffkine. 

 Stalactite bouillon cultures of plague are grown for five to six weeks. 

 These are killed by a temperature of 65 C. for one hour. Lysol (J%) is 

 added to the preparation and from 0.5 to 4 c.c. injected, according to 



