SPIROCH^TES: LIFE-CYCLE 77 



which was the less usual alternative method for cross- 

 infection in the spirochaetes of Lamellibranchs, has 

 become the usual course for the spirochsetes of the 

 blood. Commonly the formation of spores is 

 accomplished in an invertebrate, often a tick, but 

 spores also form occasionally in the blood-spiro- 

 chaetes while still within their vertebrate hosts. 

 The process of formation of spores is, in every detail, 

 like that of the molluscan spirochaetes, but on the 

 rupture of the periplast the minute spores issue 

 direct into the blood-stream, and there undergo 

 further development. We have traced the develop- 

 ment of spores in S. duttoni, S. recurrentis, and 5. gal- 

 linarum. The multiple transverse fission does not 

 appear to be an essential phase in the life-history of 

 the spirochaete when within its vertebrate host, but 

 in our opinion is really an anticipation of what 

 occurs in the invertebrate carrier. 



The history of the spirochaete granules in the 

 vertebrate host is of some interest. In 1906 

 Prowazek recorded the intracorpuscular stages of 

 S. gallinarum, the spirochaete of fowls' blood. Breinl 

 (1907) had observed S. duttoni forming granules in 

 the spleen. Balfour (1908) stated that the ovoid 

 bodies or granules formed by S. gallinarum occurred 

 within the red corpuscles of the fowls' blood. 

 Recently one of us (Fantham, 1911) observed in 

 some smears of human blood from a patient who 

 had apparently recovered from African tick fever 

 some very interesting forms of S. duttoni within the 

 red cells. The spirochaetes showed spiral bodies 

 with terminal swellings, somewhat resembling sper- 



