176 MEDICAL ZOOLOGY. 



Habitat. In fishes, particularly upon the gills, in the muscles, and be- 

 tween the coats of the eye, in the swimming bladder, etc. (Micro. Diet.) 

 In the heart and voluntary muscles of mammals, such as the cow and sheep, 

 they are often numerous. (Beale.) They have also been found within the 

 muscles and viscera of the human subject. (Lindeman.) 



Development. The entire mass increases in size as the small bodies in- 

 crease in size, probably by division and subdivision within the cyst. (Beale.) 



It is believed by some that there is an intimate relation between these 

 bodies and the causation of the cattle plague ;* but other observers, while 

 recognizing the frequency of the infection in animals dead of the disease, 

 attribute no power to the Psorospermiae.t The significance of their presence 

 in man has not been ascertained. 



GREGARINID^E, Dafour. Round, oval, fusiform, or cylindrical bodies, con- 

 sisting of a smooth transparent cell wall, enclosing a granular, more or less 

 liquid mass, with one or more nuclei and nucleoli. Sometimes they exhibit a 

 contraction in the middle, or are divided by a transverse septum. In some a 

 process resembling a head is situated at one end, and may be either naked 

 or armed with hook-like processes. Motion slow ; cilia obscurely seen both 

 upon the outer and inner surface of membrane. One or more long filaments 

 sometimes arise from the outer surface. 



Measurements. 



Habitat. 



Development. 



Two individuals coming into contact by corresponding portions of the 

 body become shortened and firmly united. A transparent capsule is next 

 formed around the two individuals, which encloses them in a cyst ; the adja- 

 cent portions of the cell membranes are absorbed, and the substance of the 

 two bodies become ultimately fused. Globules or cells are then formed in 

 the contents of the cells, which subsequently assuming the form of the genus 

 Navicula (boat-like bodies) have been called pseudo-naviculae. These, the 

 young Gregarinae, escape from the cell to complete their development after 

 a method unknown. In some cases it appears that the contents of the 

 two cells in conjugation remain distinct until the pseudo-naviculae are 



* " In my in vestigation upon the muscles of animals destroyed by the cattle plague, 

 I found these bodies in enormous numbers. While they are ordinarily found largely 

 in the muscular fibres of the sheep's heart, and to a less extent in that of the ox, they 

 are not to be detected in the best beef and mutton. On the other hand, in almost 

 every specimen of cattle plague beef which I have examined, these entozoon-like 

 bodies were present, and in many cases in immense numbers." (Beale.) 



f " In the heart of a healthy sheep which I afterwards ate, I calculated there were 

 about 1000 parasites to the ounce, and in the heart of a healthy bullock, which like- 

 wise served me for a hearty meal, the number were rather in excess of those in the 

 sheep. Altogether at two meals I could not have swallowed less than 18,000 of these 

 psorospermise." (Cobbold.) 



