NUTRITION. 253 



respect, not only individuals, but whole nations, differ from each 

 other. The Yakuts and Burats, who are remarkable for the 

 lightness of their bodies, are a sufficient example of this." 



A certain degree of excitement and use causes parts to be 

 better nourished, so that the exercise, for instance, of muscles, 

 is seen to render them larger, and disuse to cause them to waste. 

 Great excitement and excessive use exhaust and also occasion a 

 part to waste. Organs, or some one or more of their component 

 tissues, will, without very clear reasons, sometimes be over- 

 nourished, hypertrophied ; or under-nourished, atrophied; and 

 different tissues of the same organ are sometimes oppositely 

 affected. Nutrition is sometimes perverted, so that consistence, 

 or even texture, is changed. Occasionally the structure of a part 

 is changed to that of some other part is transformed: and oc- 

 casionally structures are produced altogether foreign to the body. 



" Brutes far surpass man in both the ordinary renewal of the integuments and 

 appendages, and in the extraordinary restoration of destroyed organs. The horse 

 periodically sheds its hair, the bird its feathers u , the stag its horns, the serpent 

 its cuticle, the lobster its shell and the teeth which are in its stomach." The 

 fall of the leaves of trees is an analogous circumstance. Insects not only change 

 their coats frequently, but undergo complete metamorphoses; are first worms, 

 then grubs, and finally winged beings. The crystalline lens extracted from a 

 healthy eye is speedily reproduced in cats, dogs, and rabbits ^, and probably in 

 other brutes. The extraordinary reproductive power of some brutes is almost 

 incredible. A lobster can reproduce a claw; a water-newt an extremity : Blu- 

 menbach actually observed the reproduction of the whole head with its four 

 horns in a snail, and the complete eye cornea, iris, crystalline lens, &c. in a 

 water-newt. 2 Besides greater powers of reproduction than man, brutes gene- 

 rally possess greater also of reparation will survive injuries which would prove 

 fatal to us, perhaps under any circumstances, or at least without great care. 

 I related Brunner's numerous attempts upon the life of a dog, of which, violent 



u Feathers which are not cast off, have been discovered to receive an increase 

 of colour at the moulting season. Linncean Transactions. 1818. 



* This corroborates the propriety of the view taken by Dr. Prout in an unpub- 

 lished paper written many years ago, in which he contends that the teeth are to 

 be arranged with the integuments. A similar opinion has been lately published 

 in France. 



y MM. Cocteau and Le Roy d'Etiolle. Magendie's Journal de Physiologic. 

 Janvier, 1827. 



z Guttingen Literary Notices. 1787. pp. 28. 30. 



s 



