GROWTH OF THE COCCIDIA. 211 



I have never been able to observe any further change in the 

 Coccidia within their host. A like want of success has attended most 

 of the earlier observers of Coccidia in warm-blooded animals, and that 

 whether the germs originated in the liver or in the intestine. The 

 only one who reports differently is Eimer; but the object on which 

 he bases his results is plainly different from Coccidium oviforme, and 

 cannot be directly ranked with it, as we shall afterwards see. 



But the Coccidia do not remain permanently in their hosts. They 

 pass, though indeed only to a small extent, through the communica- 

 tions which persist here and there between the nodules and the bile- 

 ducts, and reach sooner or later the gall-bladder and intestine, 

 and are finally expelled with the fseces, just as are the parasites 

 and eggs directly developed in the intestine. Having reached the 

 exterior, they undergo, like the eggs of worms (p. 54), a further de- 

 velopment, after a longer or shorter period of incubation. This was first 

 discovered by Kauffmann (1847), and since then closely studied, espe- 

 cially by Lieberkuhn, Stieda, Reincke, and Waldenburg. 1 The results 

 of the last two investigators (except the later experiments of Walden- 

 burg) apply not to the so-called hepatic Psorosperms, but to the 

 Coccidia of intestinal epithelium ; but these, unlike Eimer's specimens, 

 are forms which exactly coincide with Coccidium oviforme in all 

 essentials, if they be indeed a distinct species. 



The length of the period of incubation varies in individual cases. 

 Kauffmann observed Coccidia kept in water develop after fourteen 

 days, Stieda only after six weeks, and Leiberkiihn after months, while 

 "Waldenburg and Eeincke found Coccidia forming spores after a lapse 

 of four to five days, or less. My own cultivation-experiments, which 

 began early in February, furnished, in about a month (in a warm room), 

 the first specimens with Psorosperms. At first there were only a few, 

 but they increased in the course of the following weeks, and towards 

 the end of March the majority of the Coccidia had undergone their 

 metamorphosis. The others, which were mostly young forms, with 

 their protoplasm still diffuse, seemed to be dead. But all this was in 

 only one of my cultivations. In other bottles, which stood in a cooler 

 place, only a few specimens attained further development even after 

 nine weeks, although they still seemed, with few exceptions, quite 

 healthy. 



Like the hard-shelled worm-eggs, the Coccidia have very con- 

 siderable power of resistance, so that neither chromic acid nor 

 chromate of potassium, of ordinary strength, seem to have an in- 



1 Even in 1862 Waldenburg abandoned his early, undoubtedly somewhat imperfect, 

 observations. See his paper, " Ueber Strucktur und Ursprung der wurmhaltigen 

 Cysten," Archiv f. pathol. Anat., Bd. xxiv., p. 149, 1862. 



