CHAPTER IV. 
TORTOISES. 
HE general shape of a Tortoise is fairly familiar to 
nearly everybody. It is well called a ‘‘ Bucklered 
Reptile ” for it is effectually protected by a case or 
buckler. This buckler, in which the animal lives, somewhat 
in the same way as a snail does in its shell, is a very 
curious contrivance. The upper part of it, the carapace, is: 
chiefly formed by the dilation and union of the bones of 
the spine and ribs, and by a number of bony plates which 
grow in the skin; the lower part, the plastron, consists 
for the most part of the expansion and joining together of: 
certain dernal or skin bones. Most Tortoises have the power 
of withdrawing the head, legs, and tail under the protection of 
their shell. The Chelonians are toothless, and their jaws bear 
no little resemblance to the beak of a parrot. They all lay 
eggs, mostly with a hard, calcareous covering. 
No other vertebrate animal has greater tenacity of life than the 
Tortoise. For example, it is said that the heart of a beheaded 
Chelonian will continue to beat for hours after all blood has been 
drained from its body. It is also recorded that M. Redi deprived 
&% Land Tortoise of its brain, and the creature on being set at 
liberty crawled about as if it had hardly been injured at all, the 
only difference in its appearance was the persistent closing of its 
eyes. After the operation, it continued to live for nearly eight 
months. Another Chelonian existed for twenty-three days after 
it had been decapitated. 
