l62 MAMMALIA. 



the dirt was quietly removed. Within twenty-four hours a large and 

 handsome Brewer's Mole was found in the pipe. 



The modification of structure that adapts this animal to its peculiar 

 mode of life affords a most remarkable exatnple of animal specializa- 

 tion. The conical head, terminatino^ in a flexible cartilaginous 

 snout, and unincumbered with external ears or eyes to catch the dirt, 

 constitutes an effective wedge in forcing its way through narrow 

 apertures ; the broad and powerful hands, whose fingers are united 

 nearly to their very tips and armed with long and stout claws, supply 

 the means by which the motive power is applied, and serve to force 

 the earth away laterally to admit the wedge-like head ; while the ap- 

 parent absence of neck, due to the enormous development of muscles 

 in connection with the shoulder-girdle, the retention of the entire 

 arm and forearm within the skin, the short and compact body, and 

 the covering of soft, short, and glossy fur, tend to decrease to a 

 minimum the frictional resistance against the solid medium through 

 which it moves. In fact, it presents a most extraordinary model of a 

 machine adapted for rapid and continued progress through the earth. 



The mole does not, and cannot, dio- a hole, in the same sense as 

 other mammals that engage in this occupation, either in the construc- 

 tion of burrows or in the pursuit of prey. When a fox or a wood- 

 chuck digs into the ground, the anterior extremities are brought 

 forward, downward, and backward, the plane of motion being almost 

 vertical : while the Mole, on the other hand, in making its excava- 

 tions, carries its hands forward, outward, and backward, so that 

 the plane of motion is nearly horizontal. The movement is almost 

 precisely like that of a man in the act of swimming, and the simile is 

 still closer from the fact that the Mole brings the backs of his hands 

 together in carrying them forward, always keeping the palmar 

 surfaces outward and the thumbs below. Indeed, when taken from 

 the earth and placed upon a hard floor, it does not tread upon the 

 palmar aspect of its fore-feet, as other animals do, but runs along on 

 the sides of its thumbs, with the broad hands turned up edo-ewise. 



