ORGANS OF CHELON1A. 



595 



Some Peculiarities in the Organs of Chelonia. 



In Chelonians and in all higher animals except serpents, there are 

 twelve cranial nerves, for, 

 in addition to the usual 

 ten, a spinal accessory to 

 cervical muscles, and a 

 hypoglossal to the tongue, 

 are ranked as the eleventh 

 and twelfth. 



The gullet of the turtle 

 shows in great develop- 

 ment what is hinted at in 

 others, long horny papilla 

 pointing downwards ; it is 

 probable that these help 

 to tear up the food (sea- 

 weed in the case of the 

 turtle). 



The heart is three-cham- 

 bered, but an incomplete 

 septum divides the ven- 

 tricle into a right portion, 

 from which the pulmonary 

 arteries and the left aortic 



il 



arch arise, and a left por- 

 tion, from which the right FlG - 2 90-~ -Internal view of skeleton of turtle, 

 aortic arch issues. From ~* rom Edinburgh Museum of Science and 

 the right aortic arch, which 

 contains more pure blood /7 -' Humerus ; Sc., scapula, running dorsally ; c., 



coracoid ; e.c., epicoracoid ; p.c., precoracoid ; 



P., pubis ; il., ilium, running dorsally; ?'., 



ischium ; F., femur. 



than the left, the carotid 

 and subclavian arteries are 

 given off. The left aortic 



arch gives off the ccdiac artery before 

 it unites with the right. 



The lungs are attached to the 

 dorsal wall of the thorax, and have 

 only a ventral investment of peri- 

 toneum ; each is divided into a series 

 of compartments into which branches 

 of the bronchus open. There is a 

 slight muscular " diaphragm." The 

 filling and emptying of the lungs is 

 helped by the protrusion and re- 

 traction of the head and legs, but 

 FIG. 291. Dissection of Chelonian there are also "swallowing mO ve- 

 -After Huxley. menls- > There are no voca j chords5 



r.7'., Right half of ventricle; S., but there is sometimes a feeble 



septum ; l.v., left half of ventricle ; yoice 



r.a., right auricle; /.., left auricle; T ',, , . , 



Lao., left aortic arch ; r.ao., right . ln l ! ie males, the kidney, the epi- 



aortic arch ;/.<?., pulmonary arch. didymis, and the testes lie adjacent 



