THE ATLANTIC OCEAN. 221 



being accomplished, the sand is again scraped back 

 over the eggs, and the surface made smooth as before. 

 The sun soon hatches the eggs, and the little Turtles 

 crawling forth from the sand, betake themselves to 

 the sea. The usefulness of this animal as an article 

 of luxurious food is well known ; but its real value 

 can only be appreciated, when we view it as afford- 

 ing an immediate relief from the horrors of scurvy, 

 which, arising from the constant use of salted pro- 

 visions, has often proved so terrible a scourge in 

 long voyages. There is a peculiarity in the struc- 

 ture of the heart of this and kindred animals, which 

 is worthy of notice. In man and other warm-blooded 

 animals, the blood is brought by the veins to the 

 heart, and poured into a chamber called the right 

 auricle; a communication exists between this and 

 a second chamber, called the right ventricle; from 

 the latter the blood is forced through a large ar- 

 tery to the lungs, to be renewed by exposure to the 

 air; from the lungs it is sent through veins to a 

 third chamber of the heart, called the left auricle, 

 and thence into a fourth, called the left ventricle, 

 from which the great artery, called the aorta, carries 

 it again into the whole body. Thus, no particle of 

 the blood can be conveyed again into the system 

 without having passed through the lungs ; but in the 

 Turtle the case is different. All the four cham- 

 bers of the heart are present, but there is a commu- 

 nication open between the left and right ventricles ; 

 and the aorta and pulmonary artery both originate 

 from the right ventricle. In consequence, a part 

 only of the blood is sent thence to the lungs, which, 



T 2 



