CHAPTEK IX. 



THE pathogp:xic hemosporidia. 



Many recent students of the protozoa (e. g., Hartmann, Liihe) are 

 inclined to place the group of parasites which Danilewsky ('<^'5) named 

 hemosporidia with the mastigophora rather than with the sporozoa. 

 It is possible that future research will justify this step, and that the 

 large, relatively immobile blood parasites, like lankesterella of the 

 frog, hemogregarina of turtles and tortoises, karyolysis of lizards, 

 hemoproteus of birds, and plasmodiura of man, are, like the Leish- 

 man-Donovan bodies, only passing phases of some flagellated proto- 

 zoan, but at the present time the evidence is not weighty enough to 

 warrant such a step even as a working hypothesis. The weakness of 

 the evidence, apparent as soon as reviewed, may be briefly summarized 

 as follows: Trypanosomn nocfuce has an intracorpuscular cytozoic 

 phase; Herpetomonas donovani has an intracorpuscular cytozoic 

 phase; babesia (Piroplasma) a genus whose several species infect 

 erythrocytes of various mammals, at certain periods possesses a 

 blepharoplast (?) and gives rise to so-called "flagella;" merozoites of 

 Plasmodium vivax and of hemoproteus are said to show at times 

 rudimentary flagella (Hartmann). 



Kvidence is constantly accumulating, on the other hand, to show 

 that the full life history of hemosporidia may be completed without 

 any sign of a flagellated stage. Such is the case, for example, in 

 Hintze's account of the life history of Lanke.HterdUi rcuKirum, while the 

 incomj)lete accounts in cases of other hemosporidia give no ground 

 for assuming the occurrence of such a stage. The carefully studied 

 life history of a new genus and species of heinogregarinidjc, Hepato- 

 zooii pcniic/osum, Miller, of the rat, gives the best evidence of the 

 independent position in classification of these forms. This organism, 

 discovered by W. W. Miller,^ somewhat reseml>les Leukocytozooti 

 cduis, Bentley, of Indian dogs. In the majority of cases it causes 

 death of the infected rat, the disease being normally transmitted by 

 mites of the species Lclap.s crJiidiiiiiiis. Tlie sj)()r()('ysts are taken into 

 the digestive tract of the rat together with its mite host, and the sporo- 

 zoites (!()/« long) are lii)erated by the action of the digestive juices 

 (Fig. 1()()). The young forms penetrate the intestinal walls and enter 



'The prpinutiire dealli of lliis (jifte I younu oli-^pi\fT, liis life ;i suciiCuc to duly, w;is a -ail 

 blow to tlie cause of prolozoiiloKy in .\iiieri<'a. 



