Fig (XIII)
13.
B E C F Oöcysts (cysts) of Eimeria (Coccidium) avium. A, Oöcyst (cyst) with contents completely filling it. B, Oöcyst with contents concentrated to form a central mass. c, Commencement of division of the oöcyst contents. D, Oöcyst containing four rounded masses that will become spores. E, Oöcyst containing four sporocysts (spores). F, Oöcyst containing four sporocysts, in each of which two sporozoites have formed. droppings the contents of the cyst are in contact with the walls (Fig. 13 A), at other times they are situated in the middle (Fig. 13 B, C) of the cyst, while the contents may be at one end, or divided up into four masses (Fig. 13 D, E, F) inside the cyst-wall. The contents of the cyst are always granular (Figs. 13, 15 N). In addition to loose fæcal matters, affected birds show leg weakness, and their feathering, especially round the legs, may be poor. The flight of the young bird is also rather feeble.
The whole body of the young bird is emaciated, as shown in loss of body weight.
The presence of coccidian parasites in grouse-chicks also leads to anæmia and other alterations in the constituents of the blood, while internally there is a great increase in the size of the cæca or "blindguts." The chief source of contamination on the moors is the fæces or droppings of other diseased grouse. The droppings contain thousands of cysts (oöcysts) of the parasite, and these cysts (Fig. 13), with their hard coats, are extremely resistant, and can endure for very long periods without the death of their contents, which gradually divide to form four small sporocysts or spores (Fig. 13 E) inside. The cysts and spores are scattered over the moors by the action of the wind and rain, and, alighting on the heather or in the tarns of the moors, are taken up by the grouse in their food or drink. When the cysts are swallowed, they enter the gizzard of the bird and pass unchanged into the first part of the intestine, called the duodenum. Here the pancreatic juice is poured into the intestine to aid in digestion, and under its influence the cyst-wall is softened and dissolved, and the four small spores (Figs. 13 F, 15 R, S) (contained within the ripened cyst or oöcyst) are set at liberty. Each small spore contains two active motile germs or sporozoites (Figs. 13 F, 15 T), which emerge from the softened spore-case, and proceed to penetrate the epithelium of the duodenum (Fig. 15 A). The young parasites ultimately cause the destruction of the lining (Fig. 14) of the first part of the small intestine the region where, normally, the most active digestive processes occur. The coccidian parasites (schizonts) (Fig. 14 sch) multiply in the duodenal epithelium (Figs. 14 sch, 15 E-H), and then pass into the cæca or blind-guts," with disastrous results. 66 The life-history of Eimeria (Coccidium) avium is long and complicated. Each young parasite (Figs. 14 spz, 15 A) penetrates an epithelial cell of the duodenum, and grows (Figs. 14 par, 15 C-E) and multimz to 성 par par mz spz