120 THE NATURAL HISTORY OF 



living animal not only contain the olfactory membrane, 

 but likewise the spiracles, or organs by means of which 

 the whale is enabled to project water to a considerable 

 height above the surface of the ocean. The cerebral 

 cavity, when contrasted with the dimensions of the other 

 portions of the body, is extremely small ; beneath it is 

 the point of union of the vomer with the occipital and 

 part of the ethmoidal bones. With the exception of the 

 lower jaw-bones, all those composing the head are of a 

 spongy nature, and appear to be formed of a series of 

 laminae. The lower jaw, like the same portions of other 

 animals, and of the human infant at birth, is formed of 

 two distinct pieces of bone, united together at the point 

 or chin by symphysis, or a thin layer of intervening- 

 cartilage : each one forms a curve terminating in its 

 condyle, and measures twenty-two feet in length from 

 the chin to its articulation with the bones of the head. 

 It is extremely hard and compact ; the coronoid process 

 which is separated from the condyles by an almost hori- 

 zontal space, which occupies the place of a semilunar 

 cavity found in the other mammalia, affords insertion 

 to the temporal muscle. They articulate themselves 

 with the glenoid cavities of the occipital bone, in such a 

 manner as to form a perfect hinge joint. The superior 

 margins of these bones are perfectly smooth, and exhibit 

 not the slightest vestige of any alveolar cavities for teeth, 

 which are found in several genera of the order cetacea. 



There is a number of large foramina on the labial sur- 

 face of these bones, for the passage of large blood-vessels. 

 The anterior mental foramen is placed externally near 

 the chin, and is sufficiently large to admit a man's thumb: 

 this leads to a large canal, which traverses the body of 

 the bone ; it contains blood-vessels and nerves, which, 

 having performed their important duties in nourishing 



