l82 



GENERAL BIOLOGY 



upward about the sides of the neck. These maybe felt with 



the fingers beneath 

 the skin of the throat, 

 or moved about under 

 the skin by moving 

 the tongue with a for- 

 ceps. This part of 

 the skeleton, though 

 small and weak, is of 

 great historical im- 

 portance. These 

 paired cartilaginous 

 arches are landmarks 

 of vertebrate history: 

 to their consid- 

 eration we shall 

 have occasion to re- 

 turn later. 



The eyes of the salamander are prominent and shining 

 and they both wink at once at long intervals. If one of them 

 be touched gently, it will be withdrawn completely into its 

 orbital cavity; thus it gets out of harm's way. 



Once in a while the salamander may be seen to gulp 

 down a mouthful of air. It does not inhale; to get air 

 down it has to swallow. The air-swallowing process will 

 often be most clearly seen after the specimen has been 

 handled and put down again. On the under side of the 

 neck the pulse beat may be seen. 



On the body there is a mid-dorsal groove extending from 

 the rear of the head to the base of the tail, and there is a 

 series of costal grooves between fore and hind legs traversing 

 the sides of the body vertically. These latter are the exter- 

 nal evidence of that segmentation of the body that will be 

 found later in the vertebrae, spinal nerves and ganglia, and 



Fig 112. The branchial skeleton from the throat 

 of' the salamander, /i, the hyoid arch; / and 2, 

 latet al arms of the first and second branchial 

 arches; i, isolated basal piece corresponding to 

 the missing branchial arches. 



