-334 



ZOOLOGY 



SECT. 



R.Ao, 



FiG. 945. Diagram of heart of Turtle. 

 a, incomplete ventricular septum ; C. p. 

 cavum pulmonale ; C. v. cavum venosum; 

 L. A. left auricle ; L. ao. left aortic arch ; 

 P. A. pulmonary artery ; R. A. right 

 auricle ; s, arrow showing the course -of 

 blood in left aorta ; t, in right aorta ; 

 v. v'. auriculo-ventricular valves ; w, 

 arrow showing the course of blood in left 

 auriculo-ventricular aperture ; x, in 

 right ; y, between cavum venosum and 

 cavum pulmonale ; 2, in pulmonary 

 artery. (After Huxley.) 



the ventricle contracts, its walls come in contact with the edges of 

 the septum, and the cavum pulmonale becomes cut off from the 



rest of the ventricle. The further 

 contraction consequently results 

 in the venous blood of the cavum 

 pulmonale being driven out 

 through the pulmonary artery to 

 the lungs, while the blood that 

 remains in the remainder of the 

 ventricle (arterial and mixed) is 

 compelled to pass out through 

 the aorta. But in the Crocodilia 

 (Fig. 946) the cavity is completely 

 divided, so that there we may 

 speak of distinct right and left 

 ventricles. From the right arises 

 the pulmonary artery and the 

 left aortic arch; from the left 

 the right aortic arch only. The 

 right and left arches cross one 



-another and where their walls are in contact is an aperture 

 the foramen Panizzce placing their cavities in communication. 



The brain of Rep- 

 tiles is somewhat 

 more highly organ- 

 ised than that of the 

 Amphibia. The brain 

 substance exhibits a 

 distinction into su- 

 perficial grey layer 

 or cortex, containing 

 pyramidal nerve cells, 

 -and central white 

 medulla, not observ- 

 able in lower groups. 

 The cerebral hemi- 

 spheres are well de- 

 veloped _ in all. The FlG> 9 46 ._ H eart of Crocodile with the principal arteries 

 mid- Drain COnSlStS (diagrammatic). The arrows show the direction of the 



11 f , 11 arterial and venous currents. I. aort. left aortic arch; 



USUally OI tWO ClOSely- l.aur. left auricle; I. aur. vent. ap. left auriculo-ventri- 



aTvnrnvirnaf or! rv^ol cular a P er ture ; 1. car. left carotid ; I. sub. left subclavian ; 



-approximated OVai i, vent , i e ft ventricle ; put. art. pulmonary artery ; r. aort. 



Optic lobes ' rarelv it right aortic arch ; r. aur. right auricle ; r. aur. vent. ap. 



- r -, . . , , ' . right auriculo-ventricular aperture ; r. car. right carotid ; 



IS divided SUperilCl- *& fight subclavian ; r. vent, right ventricle. (From 



-ally into four. The 



-cerebellum is always of small size, except in the Crocodilia 

 (Fig. 947), in which it is comparatively highly developed, and 

 consists of a median and two lateral lobes. 



l.etp 



