18 Structure and Economy 



though in fishes, whose bodies have naturally a low tempe- 

 rature, this being unnecessary, the oil is differently employed, 

 and serves other interesting purposes in their economy. 



But the blubber further assists, by its elasticity, in preserving 

 the smoothness and rotundity of the body of the whale kind, 

 which animals, as we see, have not only been deprived of exter- 

 jial ears, or of other external appendages, which would tend to 

 impede their rapid progression, but even the mammae, instead 

 of assuming their usual prominent form, are so flattened and ex- 

 tended beneath the skin as scarcely to elevate the surface ; and 

 on the same principle, the testes never descend from the lumbar 

 region. 



I must now direct your attention to the very remarkable ex- 

 terior clothing of the whale. It is, in the first place, a curious 

 fact, and one which is, perhaps, peculiar to the tribe, that those 

 parts of the skin which are exterior to the blubber, in a young 

 whale, are twice as thick as they are found to be in the adult, 

 having measured an inch and three quarters in thickness. 



Now these parts are generally called, from the analogy of 

 their position only, I conceive, the cuticle, and the rete muco- 

 sum ; to preserve which supposed analogy, anatomists are 

 obliged to describe the rete mucosum of the whale as being 

 three quarters of an inch in thickness. But after a careful ex- 

 amination of the recent skin of cetaceous animals, I cannot 

 help believing that there is no analogy whatsoever between this 

 substance called rete mucosum, in whales, and that of terres- 

 trial quadrupeds. It appears to me to be a substance of a na^ 

 ture as peculiar to itself, as that of whalebone, or of ivory ; and it 

 IS here, perhaps, destined to fulfil as peculiar a part in the ani- 

 mal economy, as those substances. It is of a dark colour 

 throughout ; it takes its origin from the outer surface, and, 

 consequently, from the most dense portion of the true skin ; 

 it is of a sub-corneous texture, and consists of a dense congeries 

 of parallel vertical filaments, having a great degree of elasticity. 

 Immediately beneath the inferior surface of this substance, 

 there is a black slimy fluid which is easily separated, and which 

 is, perhaps, the only vestige of rete mucosum ; and this sub- 

 stance is covered, externally, with a thin, smooth, black cuticle, 

 which is easily split into detached horizontal laminae. 



