General Morphology and Biology. 761 



the division of the plasma body is preceded by a division of 

 the nucleus. Besides, according to the more recent investiga- 

 tions changes in generation appears to occur in the Ijody of 

 the ticks, as is indicated by the fact that certain species of 

 piroplasma are transmitted to mammals only by certain ticks, 

 and only by j)rogenies of the ticks which have sucked the in- 

 fected blood. The nature and mode of this propagation how- 

 ever is not yet sufficiently clear, as the investigations along 

 this line with various piroplasma gave variable results (fur- 

 ther information is given under the various forms of the dis- 

 ease). 



Staining. In cover glass dry preparations fixed in the air or in 

 alcohol, the piroplasmas stain uniformly with methylene blue or other 

 aqueous aniliu dyes, while the preparations which are stained with 

 one of the nuclear staining methods by Romanoswky-Ziemann, Laveran 

 or Giemsa, disclose one or more chromatin granules in the blue stained 

 plasma. 



Cultivation. Attempts at cultivation in various ways, mostly in 

 bouillon, have given only partially positive results, however, they were 

 successful in keeping the parasites alive for a time outside of the 

 animal body, and in demonstrating in them morphological changes, 

 which ar(^ considered by some observers to be stages of development 

 (see p. 766). 



The differentiation of various species of piroplasma de- 

 pends partly on the characteristic form and size, and first of 

 all on the fact that the individual species are strongly bound 

 to certain mammals, so that they cannot even artificially be 

 transmitted to other species. 



Pathogenicity and Natural Infection. With few exceptions 

 (coast fever, tropical piroplasmosis), the piroplasma may be 

 transmitted artificially w^itli the blood of an affected animal 

 containing the parasite, by subcutaneous or intravenous inocula- 

 tion, whereupon after an incubation period of several days, 

 or even several weeks they appear in the circulating blood, 

 and some species will produce the symptoms of their respective 

 disease. 



Under natural conditions all piroplasma are transmitted 

 from affected to healthy animals by ticks, and not only in a 

 purely mechanical way, but also in that not the tick which sucked 

 the mammalian blood containing the piroplasmas transmits the 

 disease, but its immediate or more remote offspring. This is 

 possibly because the piroplasma undergo in the ticks in the 

 meantime certain stages of development. Some piroplasma, 

 as those of Texas fever, the piroplasma of dogs and of sheep, 

 pass from the female ticks which suck the blood of affected 

 animals, through the eggs to the larvae, and likewise also to 

 the later forms, whereby the parasites are inoculated into the 



