244 Proceedings of Indiana Academy of Science 



The parasite was first seen (one twentieth per field) in the blood 

 stream of the guinea-pig 24 days after it had received a ten culture tube 

 dose. During the next six days trypanosomes were present although 

 for the greater part very few in numbers. The organisms then dis- 

 appeared and were not again noted until on the ninth examination after 

 which the following 12 examinations were positive. The next 23 ex- 

 aminations did not reveal the presence of the parasite except in one 

 instance when but a single individual was noted. After being present 

 fairly numerous (five per field) in the blood stream for two days, the 

 next three consecutive examinations were negative only to be followed by 

 a positive observation and again by an intermission. The next examina- 

 tion showed the organism in greater numbers (ten per field) than in 

 any other previous examination, however, upon the following examina- 

 tion the parasite had again disappeai-ed. This was followed by five 

 positive findings and four intermissions and the animal died on the 

 210th day. 



Out of the 82 examinations made after the trypanosome was first 

 observed, .32 were positive and 50 were negative during which time there 

 were 11 positive periods and ten relapses. At no time during the course 

 of the trypanosomiasis did the parasite exceed 10 per field which was 

 noted but twice. Their scanty numbers, however, were chai'acteristic 

 as will be noted in figure 1. 



One Hundred Tubes Inoadations. — Of four guinea-pigs receiving 

 such injections with generations 141 and 142 no infections followed. 

 One would naturally conclude that if a small percentage of the animals 

 became infected when inoculated with a 10 tube dose that surely at 

 least in a few instances infection would follow if the material inocu- 

 lated was tenfold. 



Ten Inoculations of One Tube. — Six animals were used for this 

 test and received generations 133 to 139 out of which one revealed the 

 presence of the trypanosome in its blood at the end of 92 days after 

 its first inoculation or .51 days after its last. It lived for 268 days never 

 .showing more than 10 parasites per field and that but once. During 

 the greater part of its existence the blood stream was free from organ- 

 isms and, as a matter of fact, although examined twice a week the 

 trypanosomes wex'e observed but five times. 



Ten Inoculations of Ten Tubes. — Animals thus inoculated again 

 .showed marked variation as to infectivity with the parasite. One of 

 the eight guinea-pigs which received a multiple of ten culture tube dose 

 developed a very chronic form of Nagana. Trypanosomes were first 

 seen in its blood seven days after the last or 70 days after the first 

 injection and as in the case of the previous guinea-pig the organisms 

 were only observed six times during the trypanosomiasis which la.sted 

 for ten days. 



SUMMARY. 



Nagana manifests itself in three distinct types: the acute; the sub- 

 acute and the chronic. 



The virulence of the trypanosome; its avenue of entrance into 



