108 THE GROUSE IN HEALTH AND IN DISEASE 



purpose of drinking, the caeca discharge themselves, and the typical soft caeca! 

 dropping, which is so frequently misinterpreted as a sign of sickness, is then 

 deposited either upon the harder dropping of the night if the bird has not 

 already moved away, or more usually somewhere in the near neighbourhood. 



During the night the main gut and the caeca appear to be engaged in a 

 divided labour. While each caecal appendix is employed in the absorption of 

 nutritious, fluid solutions from the soft mass of food within it, the lower part 

 of the small intestine is continually receiving from above more and more of the 

 mixture of soft digested pulp and hard indigestible waste matter. 



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

 Method of which regulate the opening and closing, not only of the two entrances 

 separation. j. Q ^3 caecal appendices, but also of the entrance to the upper end 

 of the rectum. 



There are no actual valves and no visible folds, but each caecum at its junction 

 with the main gut is guarded by a narrow tubular portion (Pis. xxvi. cl, c2, 

 xxvil., Fig. 4 (i), xxvni., Fig. 3 (i)) some 4 or 5 inches (102 or 127 mm.) in 

 length, which is lined by a mucosa rich in small projecting papillae, and which 

 admits nothing to the caecum except the softer parts of the pulpy mixture. 

 The pultaceous, creamy-brown pulp must be thus squeezed into these caecal 

 back-waters by the peristaltic pressure of the small intestine from above, while 

 the rectum at the same moment refuses to admit anything at all. 



Each caecum has one blind end and one end opening into the upper part of 

 the rectum. All the useful contents of the main gut must pass into the caecum, 

 and the undigested portion must pass 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 caecum is found in the condition represented 

 Manner in PI. xxviii., Fig. 3 (i), and it is obvious from this figure that the 

 cascaare 1 riddance begins by contraction of the blind end, and that it gradually 

 emptied. wor k s toward the open end. It would appear from this that there must 

 be a pause in the entrance of material to the caeca while they are evacuating 

 the waste matter. The musculature of the small intestine seems thus to act 

 intermittently but frequently, and without any long period of rest. The caecal 

 musculature, on the other hand, must have long periods of rest when the caecum 

 is full or 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 con- 



