G 



INTRODUCTORy LECTURE. 



axis, forming the centre of support to the whole frame, and from 

 which all the motive powers radiate, and tliis axial cylinder {fig- 1. v) 

 is called the " Vertebral Column ; " vertebral, as consisting of seg- 

 ments of the skeleton, which turn one upon the other, and as being 

 the centre on which the whole body can bend and rotate ; from the 

 Latin " verto, vertere,^' to turn. 



Ideal section of a Vertebrate (Mammalian) animal. 



The vertebrated animals have the nervous matter concentrated in 

 this vertebral case, which expands at certain parts, where the 

 largest currents of sensation enter, and those of volition go out ; and 

 more especially at the anterior or upper extremity, where the impres- 

 sions to be appreciated by the nervous centre are the most varied 

 and the most distinct. The expanded mass of nervous matter, at this 

 part, is called the brain {fig. 1. b), the rest of the nervous axis, the 

 spinal chord, {ch, ch) ; Avhence the highest primary group of animals 

 is called " Myelencephala," fz"om the Greek Avords signifying brain 

 and spinal marrow. The prolongations and ramifications from these 

 centres, forming the internuntiate channels of sensation and the will, 

 are the nei-ves. 



There are five special modifications of sensation in the vertebrated 

 animals, three of which have special nerves, viz. smell (ol), sight {op), 

 and hearing (««). Taste {t) appears to be less generally enjoyed 

 by the Vertebrata, and its nerve is a large branch of an ordinary 

 nerve, the fifth pair. Feeling, which, in its more exquisite degree, 

 constitutes touch, seems a common property of all those nervous fila- 

 ments, which, passing into the posterior columns of the central axis, 

 are continued to the brain. Speaking generally, such are the attri- 

 butes of the recipient or sensitive portion of the nervous axis in the 

 Vertebrated animals. They can take cognisance of all the impressing 

 powers which surround them ; as the character and resistance of the 

 surface which supports them, the flavour and fitness of the substances 

 Avhich noui-ish tlu m, the purity of the atmosphere which they breathe, 



