Enteritis in Native Animals. 443 



In the earlier stages of the cysts degeneration is much more 

 common than in the later stages, the larger cysts. Here the 

 contents show no nuclei, but simply a granular mass, which 

 •stains deeply with eosin, and with the picric acid of Van Gieson 

 ■stain. The surrounding envelope is thicker in all the earlier 

 •stages of the parasite whether degenerated or not, and often a 

 fairly distinct nucleus with definite single nucleolus of the 

 original cell can be observed, both in the degenerated and the 

 living early stages. In the earliest stage noted, the parasite 

 partly degenerated, is situated close to the nucleus, and in the 

 centre of a roughly triangular epithelial cell (4-5. 8/x by 35.4/a) the 

 protoplasm of which completely surroimds the parasite (Plate 

 LXXVII., Fig. 18). 



Unhappily, owing to the unavoidable delay in fixing, neither 

 the cell nucleus nor the nucleolus stain definitely or deeply with 

 nuclear stains. It may be therefore that these cysts are no-t 

 degenerated, but simply a still earlier stage of the parasites' 

 development than that previously described, but at present the 

 .evidence is against this supposition. 



General. 



The large cj^sts described in the kangaroo, the wombat, and 

 probably also those of the wallaby, although situated beneath 

 the niascularis mucosae, are similar in many respects to the 

 Gastrocystis gilruthi, Chatton, 1910, affecting the abomasa of 

 sheep and goats, originally discovered by one of us, and care- 

 fully studied by Ed. Chatton. These cysts, which are to be found 

 present in the glandular mucosa of the majority of ovine sto- 

 machs, and visible to the naked eye as minute elevations, are 

 composed of an envelope and contents, the latter varying accora- 

 ingto the maturity of the parasite (Plate LXXXL, Figs. 19-20). 

 The envelope is formed by a gigantic single cell (parietal cell), and 

 the external surface of the envelope or cell is provided with a 

 uniform very fine brush-like fringe " which ensures an intimate 

 contact and facilitates exchanges with the surrounding tissue."' 

 The fringe measures 7 to 9/x in thickness. The flattened and 

 greatly enlarged nucleus of the epithelial cell persists at some 

 part of the periphery and causes a notable thickening of the 



17a 



