OF THE CETACEA. 49 



whelm the animal, and yet from being specifically 

 lighter than the waters of the ocean, instead of 

 oppiessing, it buoys it up, and makes it relatively 

 lighter, and so more active. 



The fash or muscles of the Cetacea is not so 

 much like that of fish as like that of beasts, more 

 especially the stronger, such as the bull or horse ; 

 it is firm and, with some exceptions, coarse. The 

 same remark may be made respecting their osseous 

 structure ; in colour and solidity the bones resemble 

 those of quadrupeds, though somewhat less compact; 

 and they have no medullary cavity. The mamma? 

 in the herbivorous Cetacea are pectoral ; in the 

 ordinary, abdominal. Their milk is stated to be 

 very rich, and according to Messrs. Jenner and 

 Ludlow, is like cow's milk to which cream has been 

 added. ( J. Hunter ', in Phil. Trans, vol. lxxvii.446.) 



The internal structure is very much on the same 

 model as that of the other mammalia, and this 

 therefore is a sufficient reason for our not dilating 

 upon it. Some differences, however, arise from the 

 peculiarity of their circumstances, and on these we 

 shall slightly touch. 



No circumstance connected with the economy of 

 whales is more extraordinary than the long period 

 during which they can suspend the vital function of 

 respiration. In most of the mammalia the inhala- 

 tions succeed each other with great rapidity, and 

 cannot be suspended for more than a few instants. 

 In man, for example, even when at rest, they occur 

 every three seconds ; whilst this interval in the Ce- 



