88 THE ANIMAL PARASITES OF MAN 



disturbance of heart rhythm, and nervous symptoms. (6) The myxce- 

 dematous form is characterized by similar symptoms, especially by 

 considerable swelling of the thyroid body, and myxcedema of the 

 subcutaneous cellular tissue ; sometimes there is a true pachydermic 

 cachexia. (c) In the nervous form there are motor disturbances, 

 aphasia, disturbances of intelligence or signs of infantilism, athetosis 

 of the extremities and idiocy. There are also paralytic symptoms of 

 bulbar origin, disturbances of mastication, phonation and deglutition, 

 and in some cases convulsive attacks, (d) The cardiac form, charac- 

 terized by disturbance of the heart rhythm. In all these forms the 

 parasite is found at autopsy in the nervous substance, brain, bulb and 

 heart. 



Vianna (191 1) 1 has studied the histopathology of the disease. 

 Some of the chief points are : in the heart muscle destruction of 

 the sarcoplasm, followed by interstitial myocarditis; in the central 

 nervous system invasion of the neuroglia cells and inflammatory 

 reaction ; in the suprarenal capsule invasion of medulla or cortex ; 

 inflammatory reaction can also be seen in the kidneys, the hypophysis 

 and thyroid gland. 



Recently Chagas states 2 that u schizotrypanosomiasis " has been 

 found in a child 15 to 20 days old, and that Trypanosoma cruzl 

 has also been found in a foetus the mother being infected with 

 the trypanosome. The trypanosomiasis can, then, be transmitted 

 hereditarily. 



Trypanosoma lewisi, Kent, 1881. 



The trypanosome has a nucleus somewhat displaced anteriorly, about 

 one-third of the way from the anterior (flagellar) end of the body, a 

 relatively straight edge to the undulating membrane, and a rod-shaped 

 blepharoplast (fig. 37, A). It averages about 25 //, long and 1*5 /JL broad. 



Much attention has been devoted in recent years to the elucida- 

 tion of the life history of the rat parasite, Trypanosoma lewisi. It is 

 usually non-pathogenic to its host. It has been shown that the 

 trypanosome can be transmitted from rat to rat by the rat-flea, 

 Ceratophyllus fasciatns, and by Ctenocephalus canis (the so-called dog- 

 flea). (See also p. 92). The flagellate may also persist, but doubtfully 

 develop, in the rat-louse, Hccmatopinus spinnlosns. These researches 

 may now be summarized. 



Life Cycle in the Vertebrate Host. After infection of a rat, the 

 trypanosomes usually appear in the animal's blood in five to seven 

 days. This incubation period applies either to a natural or an artificial 

 infection. The trypanosomes first observed in the rat's blood are 

 diverse in form (fig. 37), being small, medium and large in size. This 

 diversity is explained by the rapid multiplication taking place. A 



1 Mem. Inst. Oswaldo Crttz, iii, p. 276. 2 Rev. Med. S. Patilo (1912), xv, p. 337. 



