588 THE TICK FEVER PARASITE, 



up well against the ground of the corpuscle. Should the mobility 

 cease either naturall}^ or artiticially by cooling below 24° C. or by 

 killing, the amoeboid parasite becomes round and often shows a 

 central point, which, together with its usual peripheral position, 

 enaVjles it to be recognised. It differs from the pseudoparasitic 

 bodies in being larger, more refractile and motile (3). It occurs 

 in the acute and chronic stages of the disease. 



Sidney Hunt and Collins describe a similar multiplicity of 

 form among bodies occurring free in the circulating blood, but 

 especially in the substance of the kidney and the spleen, where 

 they are enormously abundant. They are also found, but to a 

 less extent, in the liver. " These free bodies vary greatly in size, 

 some being no more than ^At and some as large as i the size of a 

 bovine red blood cell, which is somewhere about ^oV ^^ ^^ inch," 

 i.e., they vary from OS to 2 ju. "They vary also in form, the 

 majority being round or spherical, some pear-shaped, some oblong, 

 some sausage-like, others constricted like an hourglass and others 

 irregular. None of these forms are by any means constant, since 

 the bodies are perpetually changing their outline. They differ 

 also in respect to colour; most are colourless and highly refractive, 

 others have a 3'ellowish or even reddish-brown tinge, but there is 

 never any granular pigment. The majority appear homogeneous, 

 others dark-centi'ed, though this latter appearance may be due to 

 their high refraction. A certain proportion are motionless, liut 

 the majority are in very active movement, and may sometimes 

 be seen to work their way across the field of the microscope, 

 apparently urged along by a flagellum. The most general an'l 

 characterLstic movement, however, is neither amoeboid nor 

 locomotive, but consists of a peculiar rolling on their own axes, 

 which gives them a twinkling appearance, something like that of 

 a small bright coin as it sinks in deep water." The motility is 

 more active than with the intracorpuscular parasite. 



The amoeboid form of the parasite is larger, being from two to 

 three times the size of the smallest motile form of Celli and 

 Santori. The refrangibility is so low that it can onh^ be seen 

 Avith difficulty in some of its phases, especially when, as is often 



