MORBID ANATOMY 407 



was demonstrable. The other was negative, but a specimen takeri- the 

 following day showed the presence of this same parasite. 



•' On the day following, specimens were obtained from 12 others, all 

 chronic cases, with the result of finding this same parasite in the blood 

 of four. In three there were very few, whilst in the fourth they were 

 present in great numbers, as many as 20 could be seen in one microscope 

 field. The animal from which the specimen was taken had suffered a 

 relapse 



" It would appear that the parasite may disappear from the peri- 

 pheral circulation, or exists there in such few numbers that it is not 

 easily demonstrable, after the acute stage has passed. It would require 

 repeated blood examination to decide this point. 



" Description of the parasite. The parasite resembles a whiplike 

 worm, having much the appearance of the Trichocephalus Dispar, its 

 length is from 10 to 14 mikrons, and is from i to 1.2 mikrons in diameter 

 through its body, the neck is nearly Jj its length, tapering gradually to 

 a point representing the mouth (?). It has a limiting membrane, which 

 is well defined, the contour is in most cases symmetrical but in some 

 the body line is quite irregular. The larger part of the parasite (body) 

 contains granular material and clear spaces, which latter vary in size 

 and number ; they are ijregularly distributed, and may encroach on the 

 wall so as to cause irregular outline. The granular material does not 

 extend to the neck. 



" The parasite is actively motile, having both a vermicular (con- 

 tractile) and spiral movement. It moves forward in a very peculiar 

 manner, the long whiplike process is thrust forward by a spirillar 

 motion, followed by a contraction of the body. 



" We have not so far been able to determine its intimate structure, 

 further than the limiting membrane, and the protoplasmic substance of 

 the body. 



" Two sizes of the parasite have been seen in all the specimens ex- 

 amined, the larger appears to be more numerous, and contains consider- 

 ably more granular material than the smaller, and usually two or more 

 vacuoles. Whether these two sizes represent male and female, has not 

 been determined. We are inclined to believe from our observations, 

 that they do not represent the male and female, because we have ob- 

 served in more than half the fresh specimens, the joining of a large and 

 small parasite in such a way as to appear to be something more than 

 accidental. 



"The pathological changes caused by this parasite is a rapid de- 

 struction of the red blood cells, causing an acute anjemia. The changes 

 occur in the blood coincident to the invasion of the parasite. In one 

 horse which had been ill seven days, the red blood cells numbered 



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