THE TRYPANOSOMES OF SLEEPING SICKNESS 819 



FIG. 395. Trypanosoma gambiense. For- 

 mation of the latent stage and transforma- 

 tion of the latent stage into a trypanosome. 

 (After Guiart.) 



In the blood, trypanosomes are occasionally seen in pairs with their pos- 

 terior [aflagellar] ends crossed (Laveran and Mesnil). 



When the trypanosomes become very numerous in the blood they pass to 

 the spleen and bone marrow, and subsequently disappear from the blood of 

 the peripheral circulation. The parasite 

 assumes a new character in the spleen : a 

 deep band makes its appearance between 

 the centrosome and the nucleus and the 

 latter becomes surrounded by a vacuole, 

 the trypanosome disintegrates and is re- 

 duced to a nucleus ; this represents the 

 latent form of the parasite. The nucleus 

 soon divides, giving rise to a new centro- 

 some from which a flagellum takes origin, 

 thus a small trypanosome of the ordinary 

 appearance is produced (fig. 395) ; the 

 latent forms disappear, and the newly 

 formed parasites pass again into the blood 

 of the peripheral circulation. 



Vitality. The trypanosomes of sleeping sickness can be kept alive for 4 or 

 5 days in blood mixed with normal saline solution and kept at room tem- 

 perature. In rabbit-blood-agar the organisms live longer but no true cultures 

 have been obtained (Laveran and Mesnil). 



Experimental inoculation. Monkeys, rats, guinea-pigs, 

 rabbits, dogs, asses, horses, goats, sheep, etc. are all susceptible 

 to inoculation with Trypanosoma gambiense. 



Only certain species of monkeys are, however, susceptible 

 (Macacus rhesus, M. cynomolgus, Cercopithecus callitrichus, C. 

 ruber, C. sphinx, etc.). The Cynocephali seem to be immune: 

 exceptions have however been recorded by Thomas and Breinl. 

 The disease which follows sub-cutaneous or intra-venous 

 inoculation of the parasite into susceptible animals is very 

 similar to human trypanosomiasis. Sleeping sickness has 

 followed intra-spinal inoculation, the incubation period vary- 

 ing from 10-45 days. 



Brumpt inoculated a Macacus cynomolgus with T. gambiense 

 with the result that the monkey died in 5 weeks with all the 

 symptoms of sleeping sickness. Numerous trypanosomes were 

 found in the blood : they were strongly agglomerated by mixing 

 the blood with an equal volume of potassium citrate solution or 

 with serum from an horse, bovine animal, dog or man. 



Bruce was able to infect monkeys (Macacus rhesus and Cerco- 

 pithecus} by inoculating them either sub-cutaneously, intra- 

 venously or intra-spinally. Following the inoculation parasites 

 Stained by Laver- were found in the blood, then symptoms of disease appeared and 

 an's method (After death took place in from 2-5 months. In a few of the monkeys 

 inoculation was followed by the appearance of parasites in the 

 blood but the animals recovered without showing any symptoms. 



White rats can be easily infected and most readily by 

 intra-peritoneal inoculation. Trypanosomes appear in the blood about a 

 fortnight after inoculation. The disease lasts about 3 months : trypanosomes 

 are found in large numbers in the later stages. The animals often recover 

 and some of them, but by no means all, are immune. 



Dogs and cats are easily infected and the disease proves fatal, as a rule, 

 in 5-6 weeks. 



niuMagnflcation 

 about 2000 dia 



