Fig (XI)
9.
Two six-hooked embryos of Hymenolepis microps. On the right is shown a transverse section of the walls of the intestine of a fowl, showing Tania botriopliti embedded in the deeper layers of the intestinal wall; aa, intestinal mucosa; b, muscular layers; sp, peritoneal lining; tt, anterior ends of the tape-worms; e, mass of exudate produced by the irritation of the head of the Tænia. numbers (Fig. 8). Until some reagent is added to the contents of the intestine, these worms are practically invisible, but on add- GROUSE] dropping which comes away from the cæca.
Here they give exit to the larva (Fig. 12), m ing some fixing fluid, such as corrosive sublimate, the thick purée-like contents of this part of the intestine resolves itself into a mass of very fine delicate white threads, inextricably tangled together and so enormous in number that there seems little room left in the duodenum for the food to pass alone. The head of the worm is concealed in the crypts and furrows of the mucous membrane, and it may possibly do harm by breaking the continuity of the mucosa.
We have no sure information as to the second host of this cestode, but as a general rule the cysts of the genus Hymenolepis live in some insect or myriapod, as is shown by the fact that the adults exist in bats, insectivores, and insectivorous birds. Tapeworm cysts have recently been found in a flea by Professor Minchin, and these cysts have been shown by Mr. Nicoll to grow into Hymenolepis diminuta in the intestine of the rat. Hence the suggestion, first made by Dr. Leiper, that the fleas of the grouse may be the second host of H. microps is well worth following up. H. microps disappears from the intestine of the bird during the winter months, a fact which may depend on the habits and life-history of its second host.
NEMATODA (Thread-worms or Round Worms).
Family. STRONGYLIDÆ. 12. Trichostrongylus pergracilis. - This worm (Figs. IO, II), like the larger of the tape-worms, D. urogalli, was described by Cobbold in 1873. He regarded it, and we think rightly, as one of the most dangerous parasites of the grouse. It lives in the paired cæca, and it should be remembered that in the grouse these cæca are very long, the two together as long as the rest of the alimentary canal. They are the organs through which the digested food is absorbed into the blood, and any injury to their walls is fraught with grave consequence to the grouse. The strongyle worms are minute and transparent, but they are rendered opaque by the addition of a few drops of corrosive sublimate or acetic acid, or of alcohol. The males (Fig. 10) are about 8 mm. in length, the females (Fig. II) somewhat longer, attaining a length of IO mm. The cuticle which covers the body is ridged, and these ridges enable the animal to progress and possibly to pierce the tissue of the wall of the cæca. Within their bodies large numbers of eggs (Fig. 12) ar matured with great rapidity. The eggs pass out of the body and are found in that part of the ---m. 1.