104 THE GROUSE IN HEALTH AND IN DISEASE 



which contains the pancreas (Pis. xxvi. Pa., xxvii., Fig. 1 (e), xxvii.a, xxvni., 

 Fig. 1 (e), XLiv.), 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 uj^per 



end of the descending loop. 



The liver (Pis. xxvi. (l.), xxvii., Fig. 1 (/), xxvii.a), 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 bv 



Liver. 



little. The shape of the loop assists this admixture, since it checks 

 the immediate passage of the contents into the convolutions of the upper 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 alka- 

 line pancreatic and hepatic secretions from the liver, becomes cri-adually 



Chemical ^ . ... . o J 



action of neutralised until it is of the right reaction as well as at the right 



digestion. r ■, • r ^ t c 



temperature for the action of the digestive ferments.^ 

 In the duodenum the contents are normally almost fluid, when there arc 

 no tapeworms or threadworms present. The duodenum is, however, the 

 common habitat of Hymenolepis microjos, and of Trichosoma 



Parasites i ■ ii ■ tic fi •<■ 



found in longicollis ; and the former of these is frequently present in such 



duodenum. ' . ,. , 



large numbers as to appear like a soft, semi-sohd, creamy mass 

 completely filling the whole length of the duodenum (PI. xxviii.. Fig. 2). 



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 particular moment more than a very small amount of solid food pulp mixed 

 with the digestive fluids. The passage of the food through it is very gradual, 

 and the admixture with the alkaline digestive juices is proportionately complete. 



Normally the outward appearance of this part of the intestine is a pale 

 creamy white, and the mesenteric vessels which ramify over the peritoneal 

 surface are almost invisible. The pancreas also should be pale creamy white or 

 faintly pink (PI. xxviii., Fig. 1 {a) (e) ). 



The alkaline mixture now passes from the duodenum into the convoluted 

 upper portion of the small intestine (Pis. xxvi. (c.s.i. ), xxvii., xxvii.a, xliv., 

 Small Fig- 1 (,V))- This extends from the lower end of the duodenum to 



intestine, ^j^^ ^^^^^^^ ^^^ ^£ ^j^^ rectum (Pls. XXVI. (r.), xxvii.. Fig. 1 (A) xi.iv.), 



' Vide pp. 105, 106. 



