806 



THE FLAGELLATA 



the flea ; on the contrary, it is an exceptional and aberrant method 



(Minchin and Thomson).] 

 Appearance in the blood. In fresh blood, T. lewisi is flattened and fusiform 



and often twisted on itself. It is the most motile of all the Trypanosomes 

 and vigorously displaces the red cells : it may sometimes 

 be seen moving across the preparation like a dart with the 

 flagellum in front. Its length including the flagellum is 

 24-25/x, its breadth 1'5/x (Laveran and Mesnil). Its protoplasm 

 is finely granular; the [tropho-] nucleus is not visible but the 

 centrosome [kineto-nucleus] appears as a refractile spot to- 

 wards the posterior end. 



In preparations fixed and stained by Laveran's method 

 (p. 772) the protoplasm is stained pale blue with fine granules ; 

 the [tropho-] nucleus, oval in shape and situated in the 

 anterior one-third of the body, is stained lilac. The undu- 

 lating membrane is unstained with the exception of its free 

 thickened border which is stained lilac and is continued 

 anteriorly into the flagellum, while posteriorly it takes origin 

 from the centrosome which is stained deep violet. 



In the blood of rats which have been infected for a long 

 time only fully developed fusiform trypanosomes are seen, all 

 of the same length. 



To study the multiplication forms it is necessary to prepare 

 stained films from the blood of a rat which has been inocu- 

 lated intra-peritoneally 48 days previously. 



The peritoneal exudate, which contains numerous multiplication 

 forms during the first 2 or 3 days, is not a very suitable material 

 for the study of the cytology of the parasites. 



Before dividing, the Trypanosome increases in size, the 

 centrosome approaches the nucleus and 

 the flagellum thickens at the end which 

 is in relation to the centrosome. Soon the 

 nucleus and centrosome as well as the 

 base of the flagellum divide. The newly 

 formed flagellum separates from the 

 original one and though at first much 

 shorter than the latter, it rapidly elongates 

 while the protoplasm is dividing. The 

 young Trypanosome finally separates but 

 may again subdivide before detaching 

 itself. 



Other multiplication forms have the 

 appearance of spherical or oval bodies in 

 which the nuclei and centrosome having 

 approached each other divide (into from 

 2 to 16 parts), and the flagella at the same 

 time split into two without the protoplasm dividing : then the protoplasm 

 shows a series of notches around its periphery (rosette appearance) and 

 finally divides into as many parts as there are nuclei. The small parasites 

 resulting from the segmentation of the rosette may again in their turn 

 divide. 



Appearance in cultures. Novy and MacNeal were able to grow the organism 

 on their blood-agar medium (p. 799) : growth takes place best at the tem- 

 perature of the laboratory and is poorer at 34-37 C. These observers have 



FIG. 388. Try- 

 panosoma lewisi 

 stained by Laver- 

 an's method. 

 (After Laveran 

 and Mesnil.) 

 x about 2000 dia- 

 meters. 



^ 



FIG. 389. Trypanosoma leurisi. 

 Leishman's stain. 



1000. 



