APPENDIX. 547 



terior part of the diaphragm, somewhat higher 

 than the kidney ; the left is situated lower down, 

 by the side of the aorta, between it and the left 

 kidney. They are composed of two substances ; 

 the external having the direction of its fibres or 

 parts towards the centre; the internal seeming 

 more uixlform, and not having so much of the 

 fibrous appearance. 



The blood of animals of this order is, I believe, 

 similar to that of quadrupeds ; but I have an idea 

 that the red globules are in larger proportion. I 

 will not pretend to determine how far this may 

 assist in keeping up the animal heat ; but as these 

 animals may be said to live in a very cold climate 

 or atmosphere, and such as readily carries off heat 

 from the body, they may want some help of this 

 kind. 



It is certain that the quantity of blood in this 

 tribe and in the Seal is comparatively larger than 

 in the quadruped, and therefore probably amounts 

 to more than that of any other known animal. 



This tribe differs from fish in having the red 

 blood carried to the extreme parts of the body, 

 similar to the quadruped. 



The cavity of the thorax is composed of nearly 

 the same parts as in the quadruped ; but there ap- 

 pears to be some difi^erence, and the varieties in 

 the different genera are greater. 



The general cavity is divided into two, as in 

 the quadruped, by the heart and mediastinum. 



The heart in this tribe, and in the Seal, is pro- 

 bably larger in proportion to their size than in the 



