444 APPENDIX. 



existence, but latterly expressed his opinion that the contraction of 

 the right auricle terminated before that of the left. The contrac- 

 tion of the ventricle appeared to both of us to commence on the 

 right side, and to be followed up by that of the left side. Trie 

 close of ventricular contraction, or the commencement of diastole, 

 was accompanied by a depression of the anterior wall of the ventricle 

 towards its right side. 



The distension of the pulmonary artery followed the contraction 

 of the right side of the ventricle, that of the anterior aorta appeared 

 to follow the contraction of the left side of the ventricle ; but this 

 appearance depends probably on the earlier closure of the orifice of 

 the pulmonary artery, and the continued distension of the systemic 

 arteries. 



I attribute the less marked asynchronism of the auricular 

 contraction in this animal partly to the small amount of its blood 

 from winter fast, partly to the interventricular septum being less 

 developed than in the lizard. 



I found that by turning up the ventricle by the handle of a 

 scalpel, the prior contraction of the right auricle was quite distinct. 

 It commences at the venous or vestibular extremity, and extends 

 forward to the apex of the auricle. After the commencement of 

 contraction in the right auricle that of the left begins, but the con- 

 traction of the right ceases before that of the left. I requested Mr. 

 Turner to examine the movements in this manner, and he at once 

 detected the prior contraction of the right auricle. 



It appears to me that the blood of the right auricle diffuses itself 

 over the anterior or inferior part of the ventricle, for the whole 

 of this surface possesses a dark tint during distension. On the 

 back or upper surface, again, the dark tint is confined to the right 

 side, no doubt in consequence of the blood of the left auricle pre- 

 occupying that compartment. 



We must assume that after the ventricular systole, and until 

 the auricular blood enters, the muscular fibres remain unelongated. 

 The ventricular compartments must therefore be nearly obliterated 

 (see sections of contracted ventricle of turtle in museum), and the 

 blood from the auricles must pass through the ventricle in the 

 direction of least resistance. Now, as the right auricle contracts 

 first, the venous blood passing out of it is directed obliquely into 



