ANATOMY AND PHYSIOLOGY OF RED GROUSE 171 



that after full feeding in the evening the Grouse jugs in 

 the heather, and the process of digestion and the action of 

 the intestine proceed until there is a large quantity of hard 

 and soft food in the lower part of the small intestine ready 

 for selective absorption and separation. This separation 

 probably proceeds all night, the soft material constantly 

 passing into the caeca, and the harder waste matter passing 

 on as constantly into the rectum and out at the vent. 

 Then, early in the morning the action is reversed, the passage 

 of food down the main gut ceases because the supply from above 

 has stopped during the night when, of course, nothing has 

 been eaten. The useful part of the caecal contents has now 

 been absorbed, and is circulating in the blood, and the caecum 

 therefore contracts downward and expels all the waste matter 

 that is in it. This is confirmed by what one sees upon the moor, 

 by the absence of caecal excreta amongst the heap of formed 

 droppings passed in the night, and by the appearance of caecal 

 excreta either on the top of these heaps, or more frequently 

 in their near neighbourhood or near the early morning drinking 

 and feeding resorts. It has already been stated that the 

 Grouse feeds more or less all day ; but, as a rule, the crop is 

 found fullest in the evening. Probably digestion is sufficiently 

 rapid during the day to deal with the food almost as fast as it 

 is picked and swallowed. It may be that the caecum receives 

 matter both by day and by night, and discharges its contents 

 only in the early hours of the morning ; but' these details are 

 not easy to determine in the wild bird. 



It is easy to see how indispensable it is to the well-being 

 of the Grouse that the caeca, whose combined length nearly 

 equals that of the rest of the alimentary tract, and which are 

 responsible for the absorption of most of its food, should be in 

 good working order. It seems impossible to exaggerate their 

 importance in the bird's economy, for if they are put out of 

 action the bird may eat as much as ever and yet rapidly lose 

 flesh by sheer starvation. 



One portion of the alimentary canal remains to be mentioned, 



