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Notes on the Life-History of Trypanosoma gambiense, etc. 

 By Muriel Robertson. 



(Communicated by the Tropical Diseases Committee of the Royal Society. 

 Received September 28, — Read December 5, 1912.) 



(Abstract.) 



The following is a brief account of some of the more salient features in the 

 life-cycle of Trypanosoma gambiense. The results are drawn from a large 

 number of experiments carried out at the Mpumu Laboratory in 1911 and 

 1912. The present paper is in the nature of a very brief synopsis, and is 

 not a full account of the experiments and conclusions. 



I. Endogenous Cycle in the Blood. 



The part of the life-history of T. gambiense spent in the vertebrate — the 

 experiments were carried out with monkeys— is characterised, as is well 

 known, by a marked fluctuation in the numbers of parasites present in the 

 blood. The individuals show a wide range of variation in length and breadth. 

 During the depressed periods, the few parasites present are of the short, 

 relatively broad type. Periods of increase are characterised by the appear- 

 ance in addition of the intermediate and long slender forms. The latter are 

 the individuals about to divide. The short form may be looked upon as the 

 adult blood-type, and is usually the most numerous form present, except 

 during the periods of rapid multiplication. These periods set in regularly in 

 every revolution of the cycle during the earlier months of the disease ; their 

 recurrence is less marked in the later stages. 



The short forms appear to be responsible for carrying on the infection in 

 the Glossina, and the blood of a monkey is only infective to fly when these 

 forms are present in sufficient numbers and in a suitable physiological 

 condition, i.e. not suffering from exhaustion. Intracellular multiplicative 

 phases do not occur in the lung, liver, or spleen of monkeys. 



Rounded, non-fiagellate individuals are occasionally found in the liver and 

 lung, apparently between the cells, but it is not perfectly clear whether they 

 may not be in rare cases within the cells. They appear at the time when 

 the trypanosomes are being destroyed, before the depressed periods of the 

 endogenous cycle, but have only been found in a teeming infection examined 

 during the earlier months of the disease. These creatures are apparently 

 about to be destroyed, but their survival in very small numbers as latent 

 forms cannot be entirely excluded. 



