502 AFRICAN TICK FEVER 



insects. After this time they gradually disappeared from the 

 stomach, but were detected in large numbers in the ovaries of 

 the female ticks, where they sometimes formed felted masses. 

 He also traced the presence of the spirochsetes in the eggs laid by 

 the infected ticks, and in the young embryos hatched from them. 

 On the other hand, Leishman has failed to find any evidence of 

 spirochsetes in the tissues of ticks later than ten days after 

 ingestion of blood containing them, or in the ova laid by them, 

 or in the young ticks when hatched, though these were proved 

 by experiment to be infective. After ingestion of the blood by 

 the. ticks, he found that morphological changes occurred in the 

 spirochsetes, resulting in the formation of minute chromatin 

 granules which traverse the walls of the intestine and are taken 

 up by the cells of the Malpighian tubules ; they also penetrate 

 the ovaries and may be found in large numbers within the ova. 

 Similar granules are to.be seen in the Malpighian tubules of the 

 embryo ticks, where they are also found in the subsequent stages 

 of their life. He has abundantly proved that infection of 

 animals may be produced by inoculation with crushed material 

 containing the granules but no spirocluvtes. He accordingly 

 considers that the granules in question probably represent a 

 phase in the life history of the parasite, and that infection probably 

 occurs by inoculation of the skin with the chromatin granules 

 voided in the Malpighian secretion and not by unaltered 

 spirochsetes from the salivary glands. It is also interesting to 

 note that Balfour has found similar granules in ticks (argas 

 persicus) infected with tpirochaste gallinarwn, 



Koch also made extensive observations on the ticks in Ger- 

 man East Africa, and found that of over six hundred examined 

 11 per cent, of these insects along the main caravan routes con- 

 tained spirilla, and in some localities almost half of the ticks 

 were infected. In places removed from the main lines of com- 

 merce he still found them, though in smaller number. It has 

 also been demonstrated that in some places the ticks are found 

 to be infected with the spirilla although the inhabitants do not 

 suffer from tick fever, a circumstance which is probably due to 

 an acquired immunity against the disease. 



It is now generally considered that the sp. Duttoni is a 

 species distinct from, though closely allied to, the organisms of 

 the relapsing fevers described above. We have mentioned some 

 differences in the clinical characters of the diseases, and there 

 are also differences in the pathogenic effects of the organisms on 

 inoculation. The sp. Duttoni, for example, produces a much 

 more severe disease in monkeys, and is pathogenic to more 



