78 SOME MINUTE ANIMAL PARASITES 



matozoa. They also had a similar appearance to 

 some forms of S. nicollei as figured by Blanc, occur- 

 ring in the fluids of the body cavity of the tick, 

 Argas persicus, that carries spirochaetes from fowl to 

 fowl. 



With regard to the stages of spirochaetes in certain 

 of their invertebrate hosts, a considerable amount of 

 information has accumulated of recent years. In 

 1905, Button and Todd showed that the tick, 

 Ornithodorus moubata, was the carrier of 5. duttoni, 

 the cause of human African tick fever, and they 

 further demonstrated that the spirochaete was capable 

 of passing through the gut walls of the ticks and 

 reaching their body cavities. Also these workers were 

 the pioneers in investigating the phenomenon of 

 hereditary infection. They proved that the tiny 

 nymphs of O. moubata, so small as to be hardly 

 recognizable and resembling tiny, spiky particles of 

 sawdust, were more to be feared than their parents, 

 for while both might be equally infected, the minute- 

 ness of the nymphs rendered them far less easy of 

 detection. Markham Carter (1907) continued the 

 progress in knowledge, showing that the spirochaetes 

 multiplied by longitudinal division and broke up 

 into granules. Balfour, working at Khartoum with 

 Argas persicus, the carrier of fowl spirochaetes, showed 

 the granular phase of S. gallinarum within the tick. 



The exact method of transmission of spirochaetes 

 by ticks was first set forth by Leishman in 1908 for 

 S. duttoni. Prior to this date, it had been thought 

 that the salivary fluid of the tick was the source of 

 infection. In the early part of 1909 one of us had 



