Ixxii 



INTRODUCTION. 



bones which lodge the internal organs of hearing, and others. 

 It forms a cavity separated from the chambers of the nose, 

 the eyes, and the mouth. Contained within it, and filling it, 

 is the Brain, the substance of which passes along the whole 

 vertebral column, and terminates in the upper vertebrae of 

 the tail, so that the spinal cord is a prolongation of the 

 nervous matter of the brain. Proceeding from the brain and 

 spinal cord, pass to the organs of the special senses, and to 

 every sensible part of the body, the fine cords termed Nerves, 

 made up of minute tubular filaments, each of which filaments 

 is finer than the spider's thread, and separately invisible to 

 the unassisted eye. 



Next to the cranium are the cervical vertebrae, or bones of 

 the neck, in number 7 ; next to these are the dorsal vertebrae, 

 or bones of the back, 18 in number ; next are the lumbar ver- 

 tebrae, or bones of the loins, 5 or 6 in number ; next is the sa- 

 crum, so called, consisting of 5 vertebrae united together, and 

 forming a single piece ; and last are the caudal vertebras, or 

 bones of the tail, varying in number from 13 to 18. 



In the following figure, 1 is the lower jaw, 2, 3, 4. 5, are 



Fin. 1. 



