vi FORM AND FUNCTION 63 



keel developed only on the hinder part of its breast- 

 bone, is remarkable also for its highly muscular crop 

 with furrows and ridges 3 by means of which it squeezes 

 out the juices of leaves. In some birds the crop is 

 altogether wanting. In Cormorants, Flamingoes, and 

 Pelicans only a very small expansion, that might 

 easily escape notice, has been found. In all fish- 

 eaters it is either, as in those just mentioned, very 

 slightly developed or non-existent. The two most 

 striking points about a Cormorant's gullet are its 

 great size and its elasticity. Just below the mouth it 

 opens out to form a spacious pouch with very thin 

 walls. Below that it narrows but very slightly before 

 there comes the very small expansion representing the 

 crop, and its walls are there just a trifle thicker. 

 When the bird is lucky enough to secure a long and 

 thick fish this great tube of nearly uniform size is 

 ready to receive it. There is no contraction at any 

 point sufficient to hinder its downward progress. A 

 crop narrowing down at its lower end to a small tube 

 formed of strong walls would be out of the question in 

 a fish-eater. In diving-birds, fish have been found 

 with their heads partly digested, while upon their 

 bodies, which had not yet reached the stomach, the 

 process had not yet begun. This must inevitably be 

 so, since nothing is more remarkable than the narrow- 

 ness of the band within the area of which lie the 

 digestive glands : a fish of any length cannot possibly 

 come under the influence of the juices all at once. 

 Nearly all the stowage room for the cormorant's 

 large meals is in the ample gullet, and great demands 

 are made upon it. One of these huge feeders was 



