J4 Structure and Economy 



the whale, most obviously, by commencing with such quad- 

 rupeds as only occasionally frequent the water, in which the 

 ^n or web between the toes is short and imperfect ; and thence 

 proceeding in our examination, successively, through the 

 otters, seals, walrus, the manati, dugongs, to, lastly, the 

 >vhales, in which all the external appearance of a true hand is 

 lost, though, internally, its structure yet identifies the fin with 

 this organ. 



The tail of a large whale measures about twenty-five feet 

 across. It is composed of several layers of tendinous fibres, 

 strongly matted together within an oily membrane ; which 

 structure imparts to it immense mechanical strength : it is 

 also flattened horizontally, for the purpose of frequently and 

 suddenly forcing the creature to the surface of the water to 

 breathe ; while the tails of fishes, on the contrary, are formed 

 vertically, because their actions being performed chiefly in the 

 depths, they do not require to rise frequently to the surface. 

 But, in the whale, the tail, which is moved by immense de- 

 pressor or flexor muscles, which are inserted into it, and form 

 two large ridges beneath the body, becomes, from its enormous 

 size and power, the most destructive instrument of defence 

 with which any animal has been gifted. When whales are 

 feeding near the surface of the water, this instrument acts 

 with comparatively little force ; for their hands or breast-fins 

 are almost sufficient alone, to modify the movements of their 

 bodies, and thus they swim slowly backwards and forwards, 

 with the mouth generally wide open, and rise at each extre- 

 mity of their short course to breathe. In playing on the 

 surface, they also move in circles, and, occasionally, with the 

 agility of the salmon, they may be seen to elevate their vast 

 bulk almost out of the water ; but, when the violent impulse 

 by the tail, necessary to such an action, is differently directed, 

 they dart like an arrow downwards into unfathomable depths, 

 or, they rapidly extend their progress over vast tracts of the 

 earth's surface. 



But while we contemplate with surprise the voluntary powers 

 of this creature in its native element, how great is our amaze- 

 ment in regarding the invohmtary muscular efforts of its heart 

 and arterial system ! Mr. Hunter having first informed us, that 



