206 THE HAEMOFLAGELLATES 



the blood at any moment. Occasionally and at irregular intervals, 

 evidently following upon a period of multiplication, the Trypano- 

 somes may be fairly numerous, their appearance frequently coinciding 

 with an access of fever. At other times, they seem to vanish almost 

 entirely from the peripheral circulation ; for what reason, however, 

 is not certain. Some authorities attribute it to the rise in tempera- 

 ture, as being unfavourable to the parasites ; others think it is 

 due to the more potent operation of chemical and physiological 

 defensive agencies of the host at a higher temperature. However 

 this may be, it has long been known that certain of the organisms 

 situated, probably, in some internal, more favourable part of the 

 body can survive and give rise later to a fresh succession of 

 parasites in the blood. 1 



The main features of the illness show a general agreement, 

 whichever variety of trypanosomosis is considered; one symptom 

 may be, of course, more marked than another in a particular type. 

 The pathogenic effects are chiefly referable to disorganisation either 

 of the circulatory or of the nervous system, or of both combined. 



Fever always occurs, at some time or other, during the course of the 

 malady. Its manifestation is extremely irregular, both in character and 

 in time of occurrence, and it is, therefore, usually readily distinguishable 

 from malarial fever. There is, particularly in chronic cases, marked and 

 progressive anaemia and emaciation, leading to pronounced enfeeblement, 

 which is, in fact, the most characteristic symptom of naturally occurring 

 trypanosomosis. A common feature is the occurrence of oedematous 

 swellings in various parts, chiefly in the neighbourhood of the genitals, 

 of the abdomen, and around the eyes. The parasites are often more 

 numerous in the bloody serosities bordering these places than in the 

 general circulation. This fact is of great importance in connection with 

 the transmission of Dourine. In this disease the parasites are rare in 

 the blood, but generally numerous in the immediate neighbourhood of 

 the oedematous excoriations on the penis, so that, in coitus, they come 

 into contact with the vaginal mucous membrane of a healthy mare, 

 through which they are able to pass. 



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 sleeping- 

 sickness the Trypanosomes penetrate into the cerebro-spinal canal, and 

 .can usually be found upon centrifugalising a sufficient quantity of the 



1 Holmes (Journ. Goinp. Pathol. xvii., 1904) and, more recently, Salvin-Moore and 

 Breiiil (Ann. Trap. Med. i., 1907) consider that these resistant forms, for which the 

 latter propose the term "latent bodies," are represented by certain of the amoeboid 

 involution-forms described by Bradford and Plimmer, Laveran and Mesnil, and 

 others (cf. p. 222). 



