170 THE GROUSE IN HEALTH AND IN DISEASE 



that of the small intestine is greenish. All that is soft of 

 the food is now squeezed into the narrow openings of the caeca, 

 while all that is hard, including the indigestible part of the 

 heather fragment, the indigestible woody fibres, and the refuse 

 of the cellular tissues, is compressed into a firm, dry mass, 

 and passed straight into and along the rectum. 



The exact method of separation is due to the action of the 

 sphincter muscles which regulate the opening and closing, not 

 only of the two entrances to the caecal appendices, but also of 

 the entrance to the upper end of the rectum. 



Each caecum at its junction with the main gut is guarded 

 by a narrow tubular portion (PL xvi.) some 4 or 5 inches 

 in length, which admits nothing to the caecum except the 

 softer parts of the pulpy mixture. The pultaceous, creamy- 

 brown pulp must be squeezed into these caecal back-waters by 

 the pressure of the small intestine from above, while, at the 

 same time, the rectum remains closed and refuses to admit 

 anything at all. 



In this way all the nourishing contents of the main gut 

 pass into the caecum, and are there absorbed into the blood 

 and system generally of the Grouse, any portion still remaining 

 undigested passes out again by the same orifice. Yet the caeca 

 always appear to be filled to some extent by material from one 

 end to the other. It is only after a prolonged starvation, say 

 for twenty-four hours or more on a railway journey, that the 

 caeca are found to be partly empty, and it is obvious from 

 observation that the riddance begins by contraction of the blind 

 end, and that it gradually works toward the open end. It 

 would appear from this that there must be a pause in the 

 entrance of material to the caeca while the waste matter is 

 being evacuated. The muscles of the small intestine seem thus 

 to act intermittently but without any long period of rest. The 

 caecal muscles, on the other hand, must have long periods of rest 

 when the caecum is full and actively absorbing, and then a 

 period of activity to empty itself. But these periods of rest 

 and activity must be of very different length. It is probable 



