ANATOMY AND PHYSIOLOGY OF RED GROUSE 167 



parallel " limbs " of about equal length. These two limbs are 

 supported and held together by a mesentery which contains 

 the pancreas (PI. xvi.), a pale pink, flattened glandular 

 mass filling the space between the descending and ascending 

 limbs. This gland pours its alkaline and digestive pancreatic 

 juice and ferment into the upper end of the descending 

 loop. 



The liver (PL xvi.) also pours its alkaline, biliary 

 secretion into the upper end of the descending loop, so that it 

 is intimately mixed with the pulped food as it passes into the 

 duodenum little by little. The shape of the loop assists this 

 admixture, since it checks the immediate passage of the con- 

 tents into the small intestine. 



Digestion is now ready to go on apace. The food, when 

 being macerated and pulped in the gizzard, is distinctly acid ; 

 but, when mixed with the alkaline pancreatic and hepatic 

 secretions from the liver, becomes gradually neutralised until 

 it is of the right reaction as well as at the right temperature 

 for the action of the digestive ferments. 



In the duodenum the contents are normally almost fluid, 

 when there are no tapeworms or threadworms present. The 

 duodenum is, however, the common habitat of the tapeworm 

 Hymenolepis microps, 1 and of the threadworm Trichosoma 

 longicollis ; 2 and the former of these is frequently present in 

 such large numbers as to appear like a soft, semi-solid, creamy 

 mass completely filling the whole length of the duodenum. 

 It is only when this worm is absent, as it generally is during 

 the winter months, that one appreciates the fact that the 

 duodenum seldom contains at any one moment more than a 

 very small amount of solid food pulp mixed with the, digestive 

 fluids. The passage of the food through it is slow and gradual, 

 and the admixture with the alkaline digestive juices is propor- 

 tionately complete. 



Normally the outward appearance of this part of the intes- 

 tine is a pale creamy white, and the mesenteric vessels which 



1 Fide p. 197. 2 Vide p. 199, 



