590 



THE TICK FEVER PARASITE, 



a reproductive stage, and produce a generation of ^el•y minute 

 bodies akin to the smallest observed stage, or there may be a free 

 reproductive phase in the blood distinct from the intraglobular. 

 These phases have not been seen. 



Sidney Hunt (5) notes that in coverglass preparations of 

 advanced cases, the parasites exhibit all the stages between being 

 intra- and extracorpuscular, the corpuscles being more or less dis- 

 integraterl. -onie of the apiosoma are seen to liave a clear central 

 portion which does not stain. The pear-shaped foi'ms are of 

 various sizes, the clear portions being more marked in the larger 

 ones. Sometimes in the blood there ai'e also seen crescent- 

 shaped bodies which Dr. E. Klein, F.li.8., considered to be the 

 stage succeeding the peai"-shape, since they are presumably full 

 of young p^-^rosoma. These crescent-shaped bodies are really 

 sarcosporidia, common muscle parasites. 



Like the yeasts, the protozoa do not lend themselves well as 

 objects of study in the dry and stained condition. Yet by exer- 

 cising care, especiall}' in the choice of a fixing agent, it is possible to 

 obtain siJecimens which tell us more of the structure of the 

 parasite than can be learnt from their stud}' in the fresh condition. 

 In a number of films of dried blood* which the writer examined 

 the various recognised phases in the life history of the parasite 

 were observed. The smaller diplococcus bodies measured 0'4/li, 

 and the larger 1 /x ; l)oth intra- and extra-corpuscular forms 

 occurred. The mature forms varied in size, the difference being 

 mainly due to the vacuole which seems to increase as growth 

 proceeds much more than the other parts of the ajoiosoma The 

 staining is irregular ; the neck, the middle and the terminal 

 margin of the pear colour deeply ; the vacuole faintly or not at 

 all. In some of the coi'puscles two refractile spherical bodies 

 are observable, and careful focussing and adjustment of the light 

 revealed the shrivelled remains of the middle and neck of the 

 apiosoma. The growth in the mature form, the persistence and 

 refrangibility point to the so-called vacuole being really a capsule, 



* Kindly lent by Dr. Frank Tidswell. 



