Theoretic Representation of the Circulation in Reptiles.
But the turtle's heart is differently formed, consisting, as the annexed theoretic representation shows, of but one ventricle and two auricles, so that a mixed, or only half aërated blood circulates throughout the body, which naturally produces a torpidity of the whole vital process. Besides, the lungs of the reptiles are incapable of aërating so great a quantity of blood as ours, as their cells are much larger, thus offering less surface to the action of the air; and finally, the ribs of the turtles being immovable, they are incapable of extending the lungs, so that the animal is absolutely obliged to swallow the necessary supply of air, and to pump it, as it were, into the lungs, by contracting the muscles of the throat. Thus we see that every precaution has been taken to reduce respiration to a low standard, and prevent the evolution of heat. With this indolence of its cold-blooded circulation, the whole nature of the animal is in harmony; the bluntness of its senses, its want of intelligence, its slow movements, and its long endurance of hunger, thirst, and want of air. It leads but a drowsy dream-like existence, and yet, we may be sure, it is far from unhappy, for all its functions and organs agree perfectly one with the other, and when concord reigns, enjoyment of some kind must exist.
The turtles are distinguished from the land tortoises particularly by their large and long fin-shaped feet, and also by a longer tail, which serves them as a rudder. They have no teeth, but the horny upper jaw closes over the lower like the lid of a box, thus serving them as excellent shears, either for crushing shells or dividing the tough fibres of the sea-grass.
Green Turtle.
They are at home in all the warmer seas, but sometimes they are carried by oceanic streams far away from their accustomed haunts. Thus, in the year 1752, a Green turtle, six feet long, and weighing 900 pounds, stranded near Dieppe; and in 1778 another, seven feet long, on the coast of Languedoc. One taken on the coast of Cornwall in July, 1756, measured from the tip of the nose to the end of the shell, six feet nine inches, and the weight was supposed to be nearly 800 pounds. These few examples show us that the turtles rank among the larger inhabitants of the ocean, although they are far from attaining the fabulous proportions assigned to them by Pliny (who makes the Indians use their shells as boats or roofs), or the enormous size of some colossal extinct species, such as the fossil tortoise from the Siwala hills, preserved in the East Indian Museum, which measures twelve feet in length. They live almost constantly at sea, partly on shell-fish, like the fierce Loggerhead turtle (Testudo Caretta), partly on sea-grass, like the Green turtle (T. Midas), and only go on shore during the warmest months of the year, for the purpose of laying their eggs.
Loggerhead Turtle.
"We followed the monotonous sea-coast," says Prince Maximilian of Neuwied, in his interesting "Travels through the Brazils;" "our two soldiers, a Negro and an Indian, frequently stopping to dig turtle-eggs out of the sand, which, boiled in sea-water, used to form our evening repast. Once, while they were busy gathering drift-wood for cooking, we found at a small distance from our fire an enormous turtle busy laying her eggs. We could not possibly have met with anything more agreeable; the creature seemed to have crawled there for the express purpose of providing for our supper. Our presence did not discompose her in the least; she allowed herself to be touched, and even raised from the ground, for which purpose four men were required. During our loud deliberations on her future fate, she gave no other sign of uneasiness than a blowing sound, and continued to work slowly with her hind fins, throwing up the earth at regular intervals.