HIII.OSOI'HY 01- ZOOLOGY. 



they are speedily reproduced, and the detached fragments 

 even begin to enjoy an independent existence. 



The power of the nervous system to repair the injuries 

 it receives, or supply the loss of abstracted portions, has 

 been sometimes called in question on very insufficient 

 grounds. Its generation at the commencement of life, is 

 surely more surprising than its production at an after period. 

 But the subject has assumed a character different from 

 mere conjecture. The numerous experiments of SPALLAN- 

 ZANI and others, to prove the power of reproduction in the 

 cold-blooded animals, establish at the same time, the capa- 

 bility of the nervous system, in these animals, to reproduce 

 abstracted parts. But this power is not confined to cold 

 blooded animals. According to the experiments of Mr 

 CRUICKSHANKS * and Dr HAIGHTON f, portions of the ab- 

 stracted nerves of a dog were speedily regenerated, and the 

 nerve restored to its ordinary functions. It is probable 

 that portions of nerves are generated and destroyed perio- 

 dically in those ruminating quadrupeds which have de- 

 ciduous horns. 



Are we to conclude, from the view which we have now 

 taken, that the parts of the nervous system are homogeneous, 

 and susceptible of a certain number of similar functions; that 

 the apparently functions of each nerve depend on the organ 

 wkh which it is connected, to accessary circumstances, 

 and not to the nature of the nerve itself? The opposite of 

 all this appears to be the case. The nerves which are em- 

 ployed in sensation, obviously differ in their mode of ac- 

 tion, from those employed for the purposes of volition, and 

 hence we may reasonably conclude, that there is a corres- 

 ponding difference in structure and composition. The 

 sixmo nerve way execute both functions ; but in that case, 



Phil. Tranu. 171)5, p. 177, f ]!,. p. 190. 



