PHYSIOLOGY AND ANATOMY OF RED GROUSE 105 



where the two caeca enter it. The small intestine measures in all 35 inches 

 ( = 872 mm.); but there is a distinction to be made between the upper or 

 proximal convoluted portion which is attached to a wider mesentery, and the 

 lower or distal straighter portion (PI. xxvi. s.S.l.) which is attached to 

 a much narrower mesentery. And, while there* is probably a difference in 

 the character of the glands which form the mucosa of these two portions, 

 the chief obvious distinction is that the convoluted portion is freely moveable, 

 whereas the straight portion is so intimately folded with the long csecal 

 appendices, and so closely bound together with them in a common mesentery 

 as to be very limited in its movement. The various parts of the lower intestine 

 are shown laid out in the accompanying diagram (PI. xxvi.), while the 

 next diagrams shows them as they appear in their normal condition in the 

 body cavity of the bird (PL xxvu., Fig. 1, xxvu.a). 



Returning, however, to the changes which are being experienced by the 

 particle of food in question as it passes from the duodenum into the convoluted 

 portion of the main gut, it is first noticed that the accompanying duodenal 

 tapeworm, Hymenolepis microps, wholly disappears, and that its place is 

 taken by the much larger and more conspicuous tapeworm, Davainea L arge 

 urogalli, often in such quantity that the outward appearance of the ta P eworn] - 

 small intestine is altered to a swollen, bulky gut of a creamy white colour 

 due to the enclosed mass of tapeworms shining through the thin and 

 distended walls. 



Another point has already been noticed, namely, that the neutral or faintly 

 acid reaction of the contents of the duodenum now gradually changes to a more 

 and more markedly alkaline reaction. Hymenolepis affects a neutral medium, 

 and Davainea an alkaline medium. 



These changes in the character of the intestinal contents can, of course, be 

 easily tested by the use of litmus papers ; but when a Grouse, which has been 

 feeding upon ripe Blaeberries, Cranberries, or Crowberries with coloured juices, 

 is examined, the contents of the alimentary canal of the bird itself are found to 

 be coloured within from end to end, in such a way as to make litmus unnecessary. 

 The juices of the berries are red, and stain the tissues red wherever the acidity 

 is not overcome by alkaline digestive juices. But wherever there is a slight 

 alkalinity in the juices there the tissues are stained bluish. This is shown in 

 the accompanying figures, which are drawn directly from the dissection of a berry- 

 feeding Grouse (see PI. xxvir., Figs. 2, 3, and 4). 



