88 



The Philippine Journal of Science 



1918 



length of 33 /x to 49 /x, with a breadth of from 15 /x to 28 xi. There 

 are few, if any, data regarding the size of Coccidium cuniculi 

 cysts recovered from human cases. 



Measurements of a few cysts of our cat Isospora show a varia- 

 tion in length of from 29 p to 38 fi and in breadth of from 22 /x 

 to 29 [i, all cysts being oval. These figures do not wholly coincide 

 with measurements of cysts, presumably of the same species, 

 made by other workers. Stiles (18) reports measurements of 

 from 24 ^ to 40 /x in length and from 19 fi to 28 p in breadth, while 

 Swellengrebel(i9) gives a length of from 39 /x to 47 /x and a 

 breadth of from 26 /x to 37 /x. 



Wenyon apparently had no opportunity to measure large num- 

 bers of the cysts of his human Isospora, and measurements taken 



from the scale on his figures give a length 

 of from 27 \x to 30 /x and a breadth of from 

 12 /x to 15 /x. The coccidium of Railliet and 

 Lucet, (16) which Fantham(8) seems inclined 

 to place in the genus Isospora, was reported 

 by these writers to form cysts measuring 

 15 [x by 10 fi. Lastly Doctor Domingo's 

 Isospora of the lizard seems to measure from 

 16.5 tt to 27.6 fi in length by from 14 ^ to 23 

 /x in breadth. 



Other figures might be quoted, but it seems 

 to me that they offer us little help in our 

 problem of determining the pathogenicity of 

 the coccidia of the lower animals to man. 



And now in conclusion let me say a word 

 about the identification of these cysts. It is 

 probably needless for me to say that this department would 

 welcome the opportunity to work up any material of this nature 

 that may be sent to it. The main thing that the observer must 

 be on his guard against is the confusing of the cysts of helminths, 

 particularly the eggs of trematodes and of hookworms, with 

 coccidial cysts and vice versa. As a rule, the eggs of helminths 

 will be found to be much larger than the sporozoan cysts, but 

 there is no denying the fact that unsegmented eggs of this type 

 do bear a striking resemblance to the oocysts of coccidia, and 

 this resemblance may even extend to the early stages of segmen- 

 tation of the eggs, particularly the two-cell stage. The best 

 plan is to dilute the stool with a considerable quantity of water 

 and set a number of the cysts aside in a moist chamber for 

 two or three days. 



In the coccidial cysts the protoplasm entirely fills the cyst 



Fig 3. Cyst of Isospora 

 bigemina in an early 

 stage of development. 



