616 THE REPRODUCTIVE FUNCTIONS. 



provided only for this temporary use appears 

 from the circumstance of its falling off spon- 

 taneously in the course of three or four days 

 after it has been so employed. 



But though the bird has now gained its 

 liberty, it is still unable to provide for its own 

 maintenance, and requires to be fed by its pa- 

 rent till it can use its wings, and has learned 

 the art of obtaining food. The pigeon is fur- 

 nished by nature with a secretion from the crop, 

 with which it feeds its young. In the Mammalia 

 the same object is provided for still more ex- 

 pressly, by means of glands, whose office it is to 

 prepare milk, a fluid which, from its chemical 

 qualities, is admirably adapted to the powers of 

 the digestive organs, when they first exercise 

 their functions. The Cetacea have also mam- 

 mary glands ; but as the structure of the mouth 

 and throat of the young in that class does not 

 appear adapted to the act of sucking, there has 

 always been great difficulty in understanding 

 how they obtain the nourishment so provided. 

 A recent discovery of Geoffroy St. Hilaire ap- 

 pears to have resolved the mystery with respect 

 to the Delphinus globiceps, for he found that the 

 mammary glands of that animal contain each 

 a large reservoir, in which milk is accumulated, 

 and which the dolphin is capable, by the action 

 of the surrounding muscles, of emptying at once 



