106 THE GROUSE IN HEALTH AND IN DISEASE 



Fig. 2 shows the food contents to be blue while in the proventriculus 

 (alkaline), on reaching the gizzard (acid) they change to reddish purple, in the 

 duodenum (slightly acid to neutral) they lose much of the red tint, but it is not 

 until they enter the small intestine (alkaline) that they again resume the blue 

 colour {see Fig. 3, representing one of the coiled loops of the .small intestine), the 

 alkaline reaction continues throughout the length of the small intestine as far as 

 the lower end of the rectum (Fig. 4 (A)), where it becomes slightly more acid, and 

 the acid reaction of the caeca (Fig. 4 (?')) also causes the colour to change to a 

 reddish tone. 



In the convoluted intestine the food is in a somewhat fluid state ; and as the 



mere presence of convolutions in the intestine of any animal are evidence of 



the necessity for a retarded passage, the function of the convolutions 



Reason for _. ... . 



convoiu- in this case is obviously to hold the mixture for a sufficient length of 



tions. . . .... 



time at a certain regular temperature m order to give the active 

 digestive ferments every chance of completing their work upon the food-pulp. 

 The heather-pulp is thus altered, so far as its alterable part is concerned, into 

 a solution of assimilable food and an indigestible refuse of woody fibre. The raw 

 material here becomes the digested material ready for use by the tissues of the 

 body as soon as it can be brought to them by the agency of the circulating lymph 

 and blood. Certain harmful and poisonous products will also unavoidably 

 Elimina- appear in the Grouse's intestine as they do in the human intestine and 

 *'°/^ °f„„„ in the intestine of every livincr animal from time to time, even in the 



poisoiiuLis ^ O ' 



food. ordinary course of digestion. These, as in the human body, having 



been absorbed with the soluble food supply into the blood are then eliminated, 

 chiefly in their passage through the liver, before the mixture of good and evil 

 products can be thrown upon the general circulation. The liver in man is the 

 great eliminator of poisons produced in the intestine, and the liver in the Grouse 

 almost certainly acts in a similar way. 



There is probably some selection and some chemical alteration during the 

 passage of the food, including that part of our heather fragment which has now 

 been digested, through the mucous membrane into the blood-vessels. 



By the time the food reaches the lower and straighter portion of the small 

 intestine it is seen that much of the fluid has disappeared, the contents are 

 becoming more and more thickened, and are now converted into a semi-fluid 

 paste interspersed with woody particles. By the time that the contents reach 

 the junction of the small intestine with the rectum they have been still further 



