28 



THE FROG 



CHAP. 



which lies a white rod, made of the same soft, pulpy sub- 

 stance as the nerves, and called the spinal cord (Fig. 6, 

 sp. cd), which ends behind in a thread-like prolongation 

 (/ t), some distance in front of the thighs. It will also be 

 found that the neural canal is continued, with a • slightly 



olfl. \ 

 crbJv. I 



dien \ 

 optl. \ 

 cbbw J 

 "dbl 



tLSt. 



Fig. 6. — Dissection of a Frog in which the entire neural canal has been opened from 

 above, and the brain (ir) and spinal cord (s^. cd) laid bare. The brain consists 

 of olfactory lobes iol/'. I), cerebral hemL<:pheres {crb. A), diencephalon (difn), 

 optic lobes ip^t. /), cerebellum (cblm\ and medulla oblongata (jned. obi), which 

 will be referred to in Chapter X. The spinal cord ends in a delicate prolonga- 

 tion, the filum terminale C/I /). The nasal bones (no), eyes {e), auditory 

 re^on of the skull (aw), transverse processes of the nine vertebrae {v. t — v. 9), 

 urostyle (w. st) and ilia (it) are indicated in outline, and serve as landmarks. 

 ("After Howes, slightly altered.) 



increased diameter, into the skull, and that the spinal cord 

 becomes continuous with the brain (br\ a complex organ 

 formed of several parts, which will be referred to hereafter. 

 Geaeral Structure of tlie Limbs. — A transverse section 



