THE H2EM0FLAGELLATES. 177 



furnish a rich source whence to procure the parasites, and are doubtless the 

 result of embolism of the capillaries or small vessels by the same. 



Nervous symptoms may be only slightly noticeable (e. g. a dull and 

 lethargic tendency towards the close of the illness), or they may be strongly 

 in evidence, especially in Dourine, Mai de Caderas, and sleeping-sickness. 

 In the two former more or less general paralysis of the posterior part of the 

 body frequently sets in ; Mai de Caderas of horses in South America is, 

 indeed, often called "hip-paraplegia." In neither of these two diseases, 

 however, have the parasites been observed actually in the nervous system 

 itself, although the brain and spinal cord show considerable histological 

 alteration. But in sleeping-sickness the Trypanosomes penetrate through 

 the membranes surrounding the brain and spinal cord, and can usually be 

 found upon centrifugalising a sufficient quantity of the cerebro-spinal fluid; 

 they have also been seen, in post-mortem examination, in the lateral 

 ventricles of the brain. It is this invasion of the nervous system by the 

 parasites that marks the transition of the case from one of " T r y p an o s o m a- 

 fever" (while the parasites are confined to the blood) to one of sleeping- 

 sickness. The results of the change are soon apparent in the onset of 

 apathy, lassitude, tremor, and the other associated nervous symptoms which 

 characterise this dreadful malady. 



Death from trypanosomosis is generally due either to 

 weakness and emaciation (in chronic cases), or to blocking 

 of the cerebral capillaries by the parasites (where these are 

 abundant and the disease consequently acute and rapid), or 

 to the disorganisation of the nervous system (paraplegic and 

 sleeping-sickness forms) . Laveran and Mesnil have expressed 

 the opinion that some factor in addition to the presence of 

 the parasites themselves — especially when these are rare — is 

 requisite to explain the severe effects produced, and suggest 

 that the Trypanosomes secrete a toxine. Neither they nor 

 other investigators have, so far, been able to discover traces 

 of any such substance. In post-mortem examination the 

 most obvious pathological feature is hypertrophy of the 

 spleen, which is generally met with, and sometimes to a 

 very considerable degree. Hypertrophy of the liver, and of 

 the lymphatic glands, also occurs ; the glands in the neck, 

 inguinal region, etc., are occasionally greatly swollen, and 

 contain numerous parasites. 



The spleen and lymphatic glands are, undoubtedly, the 



