Transmission 511 



into three groups — ^those that are peculiarly slender, those that are 

 peculiarly broad, and those of ordinary breadth. The fact that 

 conjugation takes place between the first two has led to the opinion 

 that they represent the male and female gametocytes respectively, 

 while the others are asexual. All forms multiply by fission, and 

 conjugation between the gametes is observed to take place only in 

 the body of the invertebrate host. It has not yet been accurately 

 followed in the case of Trypanosoma gambiense, but there is no 

 reason to think that the organism differs in its method of reproduc- 

 tion from Trypanosoma lewisi. Prowazek found that' when rat 

 blood containing the latter organism was taken into the stomach 

 of the rat louse, Hematopinus spinulosus, the male trypanosome 

 enters the female near the micronucleus and the various parts of 

 the two individuals become fused. A non-flagellate ookinete re- 

 sults, and, after passing through a spindle-shaped gregarine-like 

 stage, can develop into an immature trypanosome-like form in the 

 cells of the intestinal epithelium, after which the parasite is thought 

 to enter the general body cavity, and, migrating to the pharynx, 

 enter the proboscis, through which it is transmitted to a fresh 

 host. 



Another form of multiplication consists in the "shedding" of 

 infective granules. This has been studied by Ranken. * The organ- 

 isms from which this is about to take place are observed to contain 

 three or four, sometimes five or six granules of small size, highly 

 refractile and spherical in shape. They are distinctly within the 

 protoplasm of the trypanosome and swing backward and forward 

 as it makes its lashing movements. When these are closely watched 

 a time comes when one of the granules shoots out. At first the 

 granule is carried about by whatever currents of fluid it happens to 

 meet, having no motility of its own, but soon a dot appears, then a 

 flagellum, and provided with means of locomotion, and now 

 having a pyriform shape, the new embryo parasite swims away. 

 Ranken thinks these granular forms develop in the internal organs 

 and has found them of pyriform shape in the liver, spleen, 

 and lungs. 



Transmission. — -It is well known that the disease does not spread 

 from person to person. In the days when African negroes were 

 imported into America as slaves, the disease often reached our 

 shores, and though freshly arrived negroes and those in the country 

 less than a year frequently died of it, there was no spread of the 

 affection to those that were acclimated. The Europeans that 

 carried the disease from Africa to England and were the first in 

 whose bloods the trj^anosomes were found, did not spread it among 

 their fellow countrymen. A case from the Congo that died in a 

 hospital in Philadelphia and came to autopsy at the hands of the 

 author, did not spread the disease in this city. 



* "Brit. Med. Jour.," 191 2, 11, 408. 



