CHELONE MYDAS. 349 



It would appear that the arteries of a tortoise (turtle) did not contract 

 longitudinally so much as the veins and mesentery. I observed that 

 when an artery was cut through, and looking upon the end of it. that 

 it consisted of an external white ring, and an internal ash-coloured one, 

 somewhat transparent. This internal coat is much softer or more 

 spongy than the other ; its fibres are principahy circular, and are very 

 elastic, but not quite so much so as the external ones 1 . I do suppose 

 that these internal fibres are muscular ; but their being elastic made me 

 suspect [the accuracy of] this: however, I found that most of the 

 muscles had a greater degree of elasticity than the muscles of other 

 animals. I found that the lower end of the mesenteric artery opened 

 into the aorta. 



Of the Lymphatics. — In a young turtle I observed the lymphatics, 

 and they had but very few valves. I could not see any lymphatic 

 glands. The absorbents pass on the inner membrane of the gut, which 

 is thin and easily separated from the outer, or muscular. They pass 

 longitudinally or in the direction of the gut, and are so numerous as to 

 be in contact with one another, forming a plexus. From this plexus 

 they send out small regular vessels which penetrate the outer coat, and 

 afterwards join and pass along with the blood-vessels 2 . 



Of the Trachea and Lungs. — The opening of the trachea is on the 

 upper surface of the tongue, something like that of a bird, which is 

 an oblong body attached by its whole under surface 3 . The os hyoides 

 is similar to that in birds. The cartilages of the trachea are circular, 

 but a little flattened : the tube divides into the two bronchi behind the 

 upper part of the heart, which thence pass into the lungs. 



The lungs are oblong bodies, almost the shape of a cow's melt. They 

 are placed in the general cavity of the abdomen close to the spine, and 

 pass backward in that direction, adhering by the inner edge, and like- 

 wise adhering to the back-shell [carapace] by more than one half of 

 their breadth, from end to end. The part that does not adhere is 

 towards the external edge, so that you can raise that edge. The upper 

 [anterior] end is thicker and somewhat broader than the lower ; and 

 adheres to the vessels, &c. at the upper part. The lower end is much 

 more than half-way down the body 4 . 



Of the Digestive Organs. — The oesophagus is large, and beset with 

 pointed bodies on its internal surface through its whole length, which 

 are of an acute pyramidal figure covered by a strong coat, which 



1 [Hunt. Preps. Phys. Series. Nos. 940, 956—962.] 



2 [lb. Nos. 850—854, 864.] 3 [lb. Nos. 1462, 1463.] 

 4 [lb. No. 1110, Chelone caretta, No. 1117, Chelone imbricata.~\ 



