"GROUSE DISEASE "PATHOLOGY 285 



Its walls are thinner than those of the intestine, and are marked by about 

 nine longitudinal whitish lines. On opening the caecum well-marked longi- 

 tudinal ridges are seen, corresponding to the lines just described. Each ridge 

 shows alternate thicker and thinner portions. Occasionally one of the ridges 

 may be seen to die away or fuse with its neighbour. They occur through- 

 out the whole length of the caecum. 1 



On examination under a Zeiss binocular microscope ( x 8 - 33) the mucous 

 membrane of a Grouse (e.g., No. 81) in which no Strongyli are present, after 

 gentle washing in a stream of water, is seen to be regularly beset with small 

 villi of uniform size, arranged closely together on the ridges, but more 

 widely separated in the depressions, where they seem to be less well developed. 

 They often appear club-shaped, more especially on the ridges, where their 

 flattened terminations, lying closely together at a uniform level, give the 

 surface a somewhat smooth and tessellated appearance (PL XLI., Fig. 5). In 

 birds caught on the moor (e.g., No. 69), apparently normal but infected with 

 Strongyli, both the ridges and the villi are much larger (PI. XLI., Fig. 6). 



The rectum is a thick walled tube of greyish white colour, about 4 inches 

 in length. 



The contents of the gut vary much in different parts. The duodenum usually 

 contains nothing but a white, slimy mucus. The intestine contains coarsely 

 divided particles of food, and occasional grits from the gizzard. The contents 

 of the caeca present a marked contrast to those of the intestine, consisting of a 

 brownish or greenish pasty mass of finely divided material. The rectum contains 

 usually only the coarser particles of food which have never passed into the ceeca. 



Duodenum. At certain seasons of the year the duodenum of every wild 

 bird examined was packed with the long thin tapeworm Hymenolepis 

 microps. They were particularly numerous from March to May, and cai changes 

 towards the end of August. Under these circumstances the contents mentwy 

 appear to consist wholly of tenacious mucus, until shaken up in 

 alcohol, when the worm becomes visible for the first time. No obvious patho- 

 logical changes, except some reddening, were seen. Trichosoma 

 longicolle was occasionally found in small numbers. 



Intestine. - - The lower half of the intestine was often found distended 

 with tangled masses of the large tapeworm, Davainea urogalli ; they 

 bear a less definite relation to season than does Hymenolepis. Portions 



1 For a fuller description of the alimentary canal of the Grouse reference may be made to chap. v. pp. 100 et seij. 



