594 APPENDICES. 



Evans stated that when he first discovered the parasite he 

 thought it was a spirillum, but very speedily on closer examination 

 arrived at an opposite opinion. 



To him the organism presented the appearance, when fresh and 

 active, of an apparently round body, tapering in front to form a 

 neck and terminating in a blunt head. Posteriorly he described a 

 tapering tail, from which there extended a long slender lash. At 

 the head end there appeared in one or two cases a circlet of 

 pseudopods, and as the body slowly died in serum it gave the 

 appearance of flattening out. After watching very closely all its 

 changes of form and movements, Evans came to the conclusion that 

 there existed on either side of the body two fin-like papillae, one 

 near where the neck began an(J the other close to where the tail 

 began. In only very few instances he was able to see the four at 

 once. He suggested that these processes were of the nature of 

 pseudopods. 



The parasite he described as extremely active in its movements, 

 with an undulatory, eel-like motion, progressing for the most part 

 head-end foremost, but occasionally moving in the direction of the 

 lash when tugging at a corpuscle. In fresh blood these organisms 

 resembled spermatozoa in colour ; but their peculiar characteristic 

 was the power they possessed of attacking and disintegrating the 

 red corpuscles. 



Occasionally two were observed to unite and swim off as one 

 body ; but the mode of union was a disputed point. Evans thought 

 that they joined with their respective heads and tails in the same 

 direction, overlapping each other; but others to whom they were 

 shown were of opinion that they fastened with their tails in 

 opposite directions. 



The parasites were not always present in the blood, but were 

 observed to come and go in successive broods. Evans referred the 

 organism to Lewis for his opinion as to its nature. Lewis arrived 

 at the conclusion that the parasite was " more nearly related to 

 that which he found in the blood of rats than to any other " ; but 

 he was of opinion at the time that they did not appear exactly 

 the same. 



Five years later Surra broke out in British Burma, and Steel 

 was deputed to investigate the outbreak. Steel confirmed the 

 communicability of the disease to dogs, horses and mules by 

 ingestion and inoculation, but he considerably supplemented Evans' 

 views as to the nature of the disease by careful thermometric 

 observations : these finally led him to regard the disease as a true 



