74 PRACTICAL PARASITOLOGY 



sandy deposit is found, which is composed entirely of numerous oocysts. 

 If normal oocysts are spread out in shallow dishes with a small 

 quantity of gall, the developmental process will be continued. The 

 oocysts will divide into four sporoblasts which, by the secretion of 

 an envelope, become changed into " sporocysts," from the interior of 

 each of which proceed two sporozoites. This developmental process, 

 which is complete in about seventy hours, may be followed under the 

 microscope by isolating single parasites and keeping them in a damp 

 chamber. To prevent decomposition a small quantity of thymol may 

 be added to the material, or it may be treated in the first instance 

 with 4 per cent, solution of potassium permanganate ; owing to the 

 extreme impermeability of its shell, the developmental capacity of the 

 oocyst will remain unimpaired. The final emergence of the sporozoite 

 from the shell is due to the influence of the pancreatic secretion. 

 This may be proved by treating oocysts containing perfect sporozoites 

 with a preparation of pancreas. The best extract for this purpose is 

 pancreatin (Dr. G. Gruebler and Co., Leipzig), a small quantity of which 

 should be dissolved in a few cubic centimetres of water, containing 

 just a trace of soda. Both oocyst and sporocyst are furnished with a 

 micropyle, which opens under the influence of the pancreatic secretion 

 and out of which the sporozoite glides. 1 In the Eimeria of the centi- 

 pede, the oocyst alone possesses a micropyle through which the 

 sporozoite escapes, while the envelope of the sporocysts is bivalved 

 and opens under the influence of the gastric secretion. 



Cover-glass preparations of the Coccidia of rabbits are made in the 

 same way as those of the other Coccidia. It is not possible, however, 

 to get satisfactory results with the staining of encysted parasites, 

 owing to the extreme impermeability of the oocystic envelope. When 

 staining with iron-hsematoxylin, counter-stain with Bordeaux red ; 

 by this means the nuclei will become black, while the granulations 

 of the macrogametes, which otherwise are difficult to distinguish 

 from the chromatic elements, are coloured red. 



Sections of coccidial lesions from the liver of rabbits have a special 

 interest, because they show the manner in which the organ becomes 

 pathologically changed. The growths should be cut out and fixed 

 whole in alcoholic solution of mercuric chloride, and sections should 

 be stained singly with hsematoxylin and eosin. It will be seen from 

 these sections that the growths are due to pronounced local prolifera- 

 tion of the infected gall-ducts, which become cystically enlarged, and 

 into the lumen of which numerous folds of proliferated wall-tissue 

 project. The oocysts of Coccides are found free in the interior of the 



1 For further details, see E. Metzner, " Untersuchungen an Coccidium cuniculi," 

 Arch. f. Protistenkunde, vol. ii, 1903, pp. 13-72. 



