42 



Journal of Applied Microscopy. 



by an animal, the capsules are digested 

 by the gastric juice, and the falciform 

 embryos which are liberated and actively 

 motile, pass into the intestines, where 

 they either affect the epithelium or pass 

 into the liver. This developmental cycle 

 provides that from each adult coccidium 

 eight new coccidia shall originate. When, 

 however, the tissue lesions are studied 

 microscopically, one is at once struck by 

 the fact that the immense number of 

 embryos found in the epithelial cells 

 could not possibly have originated from 

 this very limited multiplication, and 

 the discovery of R. Pfeiffer that certain 

 of the coccidia do not develop into the 

 adult encysted form above described, 

 but are transformed in the sporocysts, 

 seems to be a more natural process. 



According to R. Pfeiffer, a certain 

 number of the embryos increase in size 

 until they attain that of the encysted 

 form, but instead of developing the sur- 

 rounding resisting capsule, have their 

 protoplasm divided up into a large num- 

 ber of falciform ameboid embryos. In 

 conjunction with this fragmentation of 

 the protoplasm, there are numerous 

 bizarre pseudo-karyokinetic changes, 

 sometimes with resulting figures of 

 almost geometrical beauty. 



Ultimately, this sporocyst allows the 

 exodus of a varying number of free, 

 ameboid embryos which penetrate 

 epithelial cells in the neighborhood, 

 sometimes more than one entering the 

 same cell, and there perfect their exist- 

 ence as intracellular parasites. The 

 microscopic appearance of the invaded 

 tissue is of considerable interest. Each 

 cyst has a surrounding wall lined with 

 columnar epithelium, from which long, 

 villous branched processes pass inward, 

 so that a section of one of the cysts is 

 not unlike in appearance a section of 

 the fallopian tube, and a group of them 

 is somewhat suggestive of the peculiar 

 and interesting tumor known as the 

 adeno-kystoma papilliferum. When such 

 a cyst is scrutinized closely, it is 

 found that the epithelium is identical 

 with that in the neighboring bile duct, 

 and this probably led Leukhart to inves- 

 tigate the origin of the cysts with rela- 

 tion to the biliary passages. Leukhart 

 found that each coccidial cyst was noth- 

 ing more than a distended portion of 

 the bile duct, whose epithelium was 

 invaded by the parasite. 



The explanation of the villous pro- 

 cesses from the wall of the cavity is not, 

 however, so clear. Leukhart is of the 

 opinion that each cyst is probably made 

 up of a number of bile ducts, whose 

 walls of separation have disappeared, 

 and which have united to form a single 

 large cavity, and that the villi which we 



find are nothing more than the remain- 

 ing fragments of the former duct walls. 



It is, however, quite probable that 

 these productions are more the result of 

 chronic inflammation of the mucous 

 membrane, a variety of polyposis. The 

 epithelial cells of the mucous membrane 

 within these parasitic cysts are almost 

 universally invaded by the parasites, 

 which can be found in all stages of their 

 existence. The large parasites are quite 

 self-evident; they form conspicuous, 

 large, rounded granular, intracellular, 

 nucleated, protoplasmic masses. When 

 stained with hematoxylin, the nucleus 

 is not very distinct. The granules 

 become more apparent, and coarser mar- 

 ginal granules all around the periphery 

 of the parasite are noticeable. The 

 parasite in this stage varies in size from 

 that of a normal epithelial cell to that 

 of the adult form of the coccidia, and it 

 would seem from this observation that 

 the entire life history of the parasite, 

 from its stage of appearance as a falci- 

 form embryo to that of an adult encysted 

 form, is passed within the epithelial 

 cells. Indeed, here and there through 

 the cell the intracellular parasites can 

 be found developing capsules. 



It is almost impossible to differentiate 

 the small intracellular parasites from 

 the nuclei of the epithelial cells. Curi- 

 ously enough, the small parasites have 

 more distinct nuclei than the larger ones. 

 When the cell is occupied by more than 

 one parasite, they are generally of dif- 

 ferent ages. At times the parasite 

 becomes so large that the protoplasm of 

 the epithelial cell seems no longer able 

 to enclose it. The parasite, however, 

 does not separate from the cell, but 

 remains adherent to it. The ripe coccidia 

 which leave the cells accumulate 

 together with cellular debris large num- 

 bers of embryos and the encysted cap- 

 sules of the dead adult coccidia, in the 

 interior of the dilated bile duct. 



In the livers of the young rabbits, the 

 lesion described is the only one that is 

 found. In these animals the disease is 

 generally fatal, and runs an acute course. 

 In older rabbits, which also become 

 infected, but not fatally, the disease runs 

 a chronic course, and the lesions found, 

 should the animal be killed or die a nat- 

 ural death from other causes, are usually 

 much more indurated, each cyst being 

 surrounded by a considerable massing 

 of connective tissue, which has greatly 

 limited the progress of the disease. 



Microscopic sections of these old cysts 

 generally show the cavity to contain the 

 adult form of the coccidia or their empty 

 capsules. Very often atrophy of the 

 epithelium has occurred, and if the lesion 

 be very old, the rabbit having survived 



