SPIROCHETE GROUP 447 



egg yolks are removed under aseptic precautions to a sterile Erlen- 

 meyer flask. One hundred c.c. of the sterile mouse decoction is 

 mixed with these and shaken thoroughly; 5 c.c. of sterile de- 

 fibrinated mouse blood is then added. The flask is sealed to pre- 

 vent evaporation, and placed at 37 for six or eight weeks, during 

 which time the material undergoes autolytic digestion. If properly 

 prepared, the digestion is brought about wholly by autolytic 

 enzymes, and is not due to the presence of bacteria. Examination 

 of the flask at the end of the digestion should show it still to be 

 sterile. The material for inoculation is secured by removing 

 heart blood from an infected mouse, using aseptic precautions. 

 They found that the organism multiplied and retained its viru- 

 lence for forty days under these conditions. 



Life Cycle. The work of Leishman, Todd, and others indi- 

 cates that the spirochetes, when taken into the body of the tick, 

 undergo a kind of nuclear fragmentation into chromatin granules, 

 which find their way through the wall of the digestive tract into 

 the various ofgans, principally to the Malpighian tubules and the 

 ovaries. These same granules may be demonstrated in the eggs 

 of infected females, and the nymphs are able to transmit the disease. 

 Leishman believes that holding the tick at a temperature of 34, 

 or even blood heat, causes these granules to develop into small 

 spirochetes. They are exuded from the body through the coxal 

 glands and the fluid secretion of the Malpighian tubules, and gain 

 entrance to the wound caused by the tick bite after the tick has 

 loosed its hold, and not through the salivary glands. It is pos- 

 sible that a cycle of changes of this type may account for the 

 relapses that occur in the disease. 



Immunity. Leishman succeeded in establishing an active 

 immunity in a monkey that recovered from the disease by causing 

 infected ticks to feed upon it at intervals. 



Spirochaeta kochi 



This organism, causing East African tick fever, has been found 

 to be distinct from that causing the West Coast fever. To the 

 former type the name Spirochceta kochi has been given. Other 

 related types of organisms 'causing relapsing fever have been 

 described; that described by Xovy and Knapp has been called 



