134 INFECTIOUS DISEASES DUE TO PROTOZOA 



unicellular organisms found in the blood of the animals infected 

 by them. The body of a trypanosome is fusiform, provided with 

 a lateral undulating membrane, the thickened free border of which 

 terminates in the posterior part of the body in a centrosome or 

 blepharoplast and is prolonged anteriorly as a free fiagelluin. The 

 nucleus is generally in the anterior part of the body. Multiplica- 

 tion is by longitudinal division and by segmentation, which differs 

 only in that the cell body divides much more slowly than the 

 centrosome (blepharoplast) and nucleus, thus four, eight or 16 

 small trypanosomes are formed attached by their anterior ends. 

 Conjugation is at present undetermined. Trypanosoma lewisi 

 was cultivated by MacNeal and Novy in 1903. Since then several 

 other species have been cultivated by them and others. 



A positive diagnosis is made by rinding the trypanosomes. In 

 the majority of cases this may be done without difficulty by 

 making a microscopical examination of the blood of the affected 

 animal. The parasites are most numerous in the blood during 

 the febrile periods. During the intermissions the blood is virulent 

 though the parasites may be so few as to escape even a careful 

 microscopical examination. Several preparations should be made 

 and carefully searched. The blood may be examined in the fresh 

 condition for living parasites, or smears may be made and stained, 

 preferably by one of the modifications of the Romanowsky method. 

 When the parasites are scarce it is of advantage to centrifuge the 

 blood or fluid to be examined. If blood, the red corpuscles may 

 be rendered invisible by the addition of dilute acetic acid (one- 

 third per cent, glacial). If the organisms are not found the exam- 

 ination should be repeated each day for several days. Consecu- 

 tive examinations each day for six or seven days will usually 

 reveal the parasites; but in some cases their presence is more 

 easily determined by inoculating a susceptible animal with some 

 of the blood (from a few drops to one cc.) of the suspected case. 

 Mice, rats or dogs are the most susceptible to nearly all of the 

 trypanosomes (not for Tr. theileri), the disease running an acute 

 course in them. The parasites will be found in large numbers in 

 I hi' blood of these animals inoculated with blood or infective 

 material containing pathogenic trypanosomes. 



At the present time opinions differ as to whether the disease 

 occurring in different countries is caused by different species of 



