GENERAL CLASSIFICATION OF POISONOUS SNAKES 15 
resistant substances rapidly takes place. The very bones are dis- 
solved, and the feces, which are voided some days later, contain 
only a few osseous remains and a felt-like material composed of 
hair or feathers. 
Scales.—The skin of snakes, which is very elastic and extensile, 
is covered with scales, small on the back, and in great transverse 
plates on the entire ventral surface. 
Fic. 14.—ARRANGEMENT OF THE SCALES OF THE HEAD IN ONE OF THE POISONOUS 
Colubride (Naja tripudians, or Cobra-di-Capello). (After Sir Joseph Fayrer.) 
The shape and dimensions of the scales of the head are highly 
characteristic in each species. It is therefore necessary to know 
their names and the arrangement that they exhibit: these details 
are shown with sufficient clearness in figs. 13 and 14. 
Coloration.—The colouring exhibited by the scales of snakes 
is governed generally by the biological laws of mimicry. It 1s 
therefore not a character of specific value, and may be modified 
several times in the course of the existence of the same reptile, 
according to the surroundings in which it is obliged to live. 
