430 DISSECTION OF THE PIGEON 



contains within itself sufficient nutriment for the develop- 

 ment of the chick up to the time of hatching : and all that 

 is necessary to ensure development is that the egg, after it is 

 laid, should be kept at about the temperature of the parent's 

 body. This is in most birds effected by incubation, a task 

 usually fulfilled by the hen bird, but sometimes wholly or 

 in part by the cock. 



The food of the pigeon consists largely of hard seeds, and 

 small stones are swallowed with it. 



Pigeons should be hilled with chloroform, otherwise the 

 lice with which they are invariably infested may prove a great 

 ny,isance. Before the dissection is commenced, the bird should 

 be thoroughly plucked, with the exception of one of the wings, 

 on which the feathers may be left till later. 



I. EXTERNAL CHARACTERS. 



Excepting the lower joints of the legs and the toes, nearly 

 the whole surface of the body is covered with feathers. 



A. The Main Divisions of the Body. 



1. The head is elongated antero -posteriorly, and produced 



in front into a pointed horny beak. 



At the base of the beak is a naked swollen patch 

 of skin, the cere. 



At the sides of the head are the large eyes, each 

 provided with upper and lower lids, and with a 

 well-developed third eyelid, or nictitating mem- 

 brane, a semi-transparent fold of skin which can be 

 drawn across the eye from its anterior angle with 

 great rapidity. 



2. The neck is very long and flexible. 



3. The trunk is deep dorso-ventrally, and somewhat com- 



pressed from side to side. Along the mid-ventral 

 line is a prominent ridge, formed by the ventral 

 border of the carina, or keel of the sternum. 



Posteriorly the trunk ends in a short blunt tail. 



