TRYPANOSOMA GAMBIENSE 527 



in the blood-stream in very small numbers, they may be found in the 

 lymph channels in any part of the body in greater numbers. They do not 

 appear to be intracellular, but can be found between the cells of the brain, 

 heart, stomach, kidney, and, in fact, any organ of the body where small 

 patches, probably of an oedematous nature, occur in which the trypano- 

 somes are considerably more numerous than elsewhere (Fig. 221, B). 

 Similar results were previously obtained by Wolbach and Binger (1912), 

 who studied the distribution of T. gavnhiense in rats, guinea-pigs, 

 and monkeys, and by Yorke (1911) in the case of T. brucei (T. rhodesiense) 

 in goats. 



Stevenson (1922) examined the brain of a fatal case of sleeping sickness 

 in which trypanosomes had not been seen in the blood for many months, 

 though careful search had been made. There was a high degree of round- 

 celled infiltration of the vessels of the brain, and trypanosomes could be 

 demonstrated in the intercellular spaces of the brain substance (Fig. 221). 

 These observations seem to indicate that the site of election of the try- 

 panosomes is not the actual blood-stream itself, but rather the lymphatic 

 channels. In this connection it is of interest to note that abstraction of 

 fluid from lymphatic glands as a means of discovering trypanosomes more 

 readily than in the blood was first advocated by Greig and Gray (1904) as 

 a means of diagnosing the disease in man. Clapier (1921) observed try- 

 panosomes in large numbers in the fluid abstracted from hydroceles and 

 Newham (1919) in peritoneal exudate. 



In the case of heavy infections in experimental animals, smears from the 

 spleen, bone marrow, or other organs may show trypanosomes in an intra- 

 cellular position. This is a result of phagocytosis, and the trypanosomes 

 are quickly destroyed. Phagocytosis of this kind occurs in the case of 

 other trypanosomes, and the process as it occurs m vitro in the case of 

 T. lewisi was described by Laveran and Mesnil (1904). In the process of 

 digestion the trypanosomes assume various forms which must not be 

 mistaken for developmental stages. The trypanosomes which occur in 

 the cerebro-spinal fluid of human beings in sleeping sickness often have a 

 curiously abnormal shape. 



There appear to be no data to indicate how early in the disease trypano- 

 somes enter the cerebro-spinal fluid. Broden and Rodhain (1908) state 

 that the degree of involvement of the central nervous system can be 

 gauged by the cell content of the cerebro-spinal fluid, A normal fluid 

 contains not more than three lymphocytes per cubic millimetre. In the 

 earliest stages of involvement there is an increase in the lymphocytes. 

 Later there appear medium-sized mononuclear cells, and still later large 

 vacuolated mononuclear cells. In a series of cases which were clinically 

 in an advanced stage Pearce (1921) found the number of cells in 1 c.mm. 



