120 THE STORY OF REPTILE LIFE. 



remarkable structural modifications which they 

 have undergone for the purpose of swallowing 

 their victims. 



Since it is the practice, in all save a few ex- 

 ceptional cases, among the snakes to swallow 

 their prey whole and this prey is generally of 

 large size, the circumference of the victim being 

 much greater than that of the captor the bones 

 of the jaws have acquired an unusual elasticity 

 of movement. This has been attained by substi- 

 tuting elastic ligaments for the usual inflexible 

 joints between the different bones which make 

 up the jaws. When the food is seized, the 

 process of swallowing is not, like that of other 

 animals, performed by forcing the prey down the 

 mouth and into the body, but rather, the creature 

 seems to draw itself over its prey and slowly to 

 envelop it. The sternum and shoulder girdle 

 being absent the ribs are free to expand to any 

 extent, and hence the region of the chest offers 

 no restrictions to the size of the morsel 

 swallowed. 



The work of swallowing appears to be a purely 

 mechanical one, a fact which sometimes leads to 

 " regrettable events." A case in point occurred 

 some eleven years since (October 1892), in the 

 gardens of the Zoological Society of London. 

 Mr A. D. Bartlett relates how, on the evening of 

 that fatal day, two pigeons were placed in the 

 cage containing two fine specimens of Boa con- 

 strictors, one of the birds being immediately 

 seized, the keeper left the house. Eeturning 

 next morning he found that one of the snakes 

 had disappeared. A glance at the remaining 



