810 THE FLAGELLATA 



Infection of susceptible animals is very easily effected by inoculating a 

 trace of blood-stained serous exudate or a few cubic centimetres of infected 

 blood sub-cutaneously, intra-peritoneally or intra-venously : it is sufficient 

 even to place a drop of the blood-stained exudate on a superficial excoriation 

 of the skin or on an uninjured mucous membrane to infect the animal. 

 Attempts at infection by ingestion have always failed. In one instance 

 the seminal fluid of a rabbit contained the parasite and the animal infected 

 an healthy doe by the genital passage (Rouget). 



Mice. White rats. In these animals the parasite rapidly becomes general- 

 ized : mice die in 5-6 days, the blood and internal organs swarming with 

 trypanosomes. Infection cannot however be obtained in every case and the 

 results vary with trypanosomes from different sources : many strains fail 

 altogether to produce an infection. 



Rabbits. In infected rabbits the trypanosomes are found only inter- 

 mittently in the blood. The animals suffer from an irregular fever, but 

 there is no relation between the paroxysms of fever and the occurrence of 

 trypanosomes in the blood. The rabbits exhibit certain characteristic 

 symptoms; for instance, oedema and sloughing of the ear, muco-purulent 

 conjunctivitis, swelling and sloughing of the external genitalia, paraplegia 

 and cachexia. Death takes place after 2-4 months. 



Horses. About the fourth day following the sub-cutaneous inoculation 

 of the parasite, there is an oedematous infiltration of the cellular tissue about 

 the site of inoculation ; the exudate contains numerous leucocytes and some 

 feebly motile trypanosomes which however are larger than the parasites 

 found in films of the blood. About the sixth day the nuclei of the trypano- 

 somes are seen to be divided into two or three masses : then the oedema 

 increases rapidly and forms a tumour containing a blood-stained exudate 

 in which the parasites are present in considerable number. 



According to Schneider and Buflfard, the trypanosomes found in the exudate are 

 of various shapes. 



1. Adult trypanosomes similar to those just described. 



2. Large, pyriform, non-motile bodies with appendices not unlike the posterior 



segments of the trypanosomes : this V-shaped form which, seen from above, 

 is like a comb or a squid represents longitudinal division of the parasite 

 and is similar to the figures seen in Trypanosoma lewisi. 



3. Trypanosomes arranged in pairs or groups of four radiating from a central 



point like a star and formed by the meeting of their posterior ends : this 

 represents a later stage of longitudinal fission. 



The parasites in the exudate begin to diminish in number from the eighth 

 to the tenth day and, together with the oedematous tumour, soon disappear. 

 The developmental cycle of the trypanosome lasts about a week. 



After this the parasites are present only in small numbers in the peripheral 

 blood, but occur in large numbers in the plaques which now soon make their 

 appearance. 



Schneider and Buffard think that the plaques seen in dourine are due to a secondary 

 multiplication of the trypanosomes in the capillaries of the skin where they are 

 arrested and that the young forms resulting from this division reinfect the blood 

 stream : " the hsemorrhagic foci and areas of softening found in the central nervous 

 system are also produced by the migration of the trypanosome into the medullary 

 vessels which it blocks and perforates." 



Asses. Asses are less susceptible to the parasite of dourine than horses : 

 the succession of forms is less regular, and the swelling assumes considerable 

 proportions from the first ; when the oedema subsides, the parasite passes 

 into the general circulation. The trypanosomes which are present at first 

 in large numbers in the blood soon become fewer and fewer : then, 6-8 days 



