28 



THE FROG 



CHAP. 



cord (sp. cd), which ends behind in a thread-like prolong- 

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

 also be found that the neural canal is continued, with a 

 slightly increased diameter, into the skull, and that the 

 spinal cord becomes continuous with the brain (br), a 



v.i 



ttst 



FIG. 6. Dissection of a Frog to which the entire neural canal (n. c) has been opened 

 from above, and the brain (br) and the spinal cord (sp. cd) laid bare. The brain 

 consists of olfactory lobes (olf. I), cerebral hemispheres (crb. h), diencephalon 

 (dien), optic lobes (opt. I), cerebellum (cblm), and medulla oblongata (med. obi), 

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

 longation, the filum terminale (/. t). The nasal bones (no), eyes (e), auditory 

 region of the skull (au), transverse processes of the nine vertebras (v. i v. g), 

 urostyle (u. st) and ilia (il) are indicated in outline, and serve as landmarks - 

 (x If.) (After Howes, slightly altered.) 



complex organ formed of several parts, which will be 

 referred to hereafter. 



General Structure of the Limbs. A transverse section 

 cut across one of the legs, at about the middle of 

 the thigh, will show in the middle of the cut surface the 



