56 KAMBLES OF A NATURALIST. 



itself sufficient to set aside in a distinct category, as 

 it were, all those animals in which such a deficiency- 

 is definitely established, but the number of these 

 animals is very limited. In proportion as we care- 

 fully study the most apparently degraded animals, we 

 discover more and more traces of the existence of 

 this system in the greater number of them. Cuvier 

 had admitted its presence in the animals which were 

 classed by him in his first three divisions of the 

 animal kingdom, but he denied its existence, or re- 

 garded it as present in mere traces, in all the Ra- 

 diata. It is now some years since MM. Tiedemann *, 



of the Invertebrata, two distinct nervous systems. One of these 

 systems has for its centre the brain and the spinal cord, and the 

 nerves which issue from it are called nerves of animal life, which 

 exclusively preside over the functions of sensibility and voluntary 

 motion. The other nervous system, which is called the system of 

 the great sympathetic, has for its centres ganglia, varying in number 

 and size, which in all the Vertebrata are situated in the abdomen. 

 The nerves which emanate from hence are called the nerves of 

 vegetative life, and they preside over the involuntary movements 

 which occur throughout the whole body, and do not communicate any 

 sensibility to the organs. These nerves, which are very numerous, 

 and much ramified, everywhere accompany the vessels, and it is 

 probable that it is under their influence that the phenomena of 

 nutrition are accomplished. 



* Professor Tiedemann, who is a foreign associate of the Institute, 

 is one of the most illustrious representatives of science in Germany. 

 He for a long time occupied a Professor's chair at Heidelberg, where 

 his reputation attracted a crowd of students from all countries, and 

 he now lives in retirement at Frankfort. We owe to him a large 

 number of anatomical and physiological works, among which we 

 shall more especially mention his different Monographs on the 

 Brain of Man, the Apes, and certain other Mammals, his treatises 

 on Zoology and Physiology, his Anatomy of the Echinodermata, 

 which received the prize awarded by the Institute, &c. 



