METABOLISM 



297 



Figure lyi. Model of ridges and papillae whereby 

 the dermis of a Rorqual is held fast to the 

 epidermis. {Schumacher, igji.) 



apart. In fact they are joined much hke dovetails, with the dermis pro- 

 jecting into the epidermis by means of a great number of longitudinal 

 ridges (Fig. 171). Moreover, every ridge is provided with a host of tall 

 papillae which reach far up into the epidermis where their tips are slightly 

 swollen (Fig. 172). In this way there is a very solid and yet elastic con- 

 nexion between the t^vo layers, while, thanks to the papillae, the capillaries 

 in them can be brought nearer the svuface of the skin. It is also quite 

 possible that the ridges and the papillae may act as touch receptors (see 

 Chapter g). 



Below the whale's dermis lies the blubber, which may be compared with 

 another subcutaneous fatty layer - bacon. The relatively tough blubber 

 is separated from the fascia covering the muscles beneath by a layer of 

 loose connective tissue. In this way the blubber can be moved indepen- 

 dently, just as, for instance, our own skin can be moved across the muscles. 

 Hence the blubber can generally be pulled off fairly easily with a winch, 

 and the flensing knife is only an auxiliary tool in removing it. The blubber 

 itself is constructed of hard and fibrous connective tissue which fuses 

 imperceptibly into the connective tissues of the dermis. Individual bundles 

 of abrous connective tissue are segregated by large concentrations of fat cells. 



The number and arrangement of the cutaneous blood vessels play a 

 most important part in maintaining the body's temperature. Parry (1949) 

 who has examined this problem thoroughly in a Fin Whale and a porpoise 

 found that the capillary network in their skins was constructed much more 

 simply than that of man and many other mammals, in whose dermis we 

 find two nets of arteries and four nets of veins. In Cetaceans, the blubber 

 is crossed by simple arterioles which pass straight to the dermis, and there 

 is no network at all. In the dermis, these arterioles run along the bottom 

 of the ridges from which a tiny blood vessel enters each papilla, there to 

 branch out into a capillary network that is most prominent in the distended 

 tips (Fig. 172). 



