MAMMALIA. 5 



but support the weight of the animal : it has very little to do with its 

 motion. 



Fowls seem to have more bone in them than either fishes or qua- 

 drupeds, and it is very evident why it should be so ; because they are to 

 have strength enough not only to stand upon the ground and support 

 themselves against gravitation and self-attraction ; but to move them- 

 selves through a medium much lighter thau themselves by means of that 

 medium, and to overcome the attraction of the earth. This requires 

 strength and firmness of body for the wings to act upon. 



[Class Mammalia.] 

 Of the Skeleton. 



All quadrupeds have seven vertebras to the neck, and generally five 

 to the loins ; but the monkey has six. The back is not so determined, 

 as some have more ribs than others. Bones are not a basis to all 

 animals : there are, perhaps, more without than with them. 



The fore- and hind-feet in quadrupeds are more like one another than 

 the hand and foot are in the human. The thumbs of quadrupeds are 

 not a counterpoise to the fingers as in the human and monkeys, but to 

 supply the place of these they have claws, as the lion, &c. ; and those 

 that have not long claws for holding generally make use of both hands, 

 as do bears, raccoons, &c, or [they avail themselves of] some resisting 

 power, as by holding something between their feet and the ground, &c, 

 as the dogs do. 



Of the Pericardium, Heart, Thorax, fyc. 



Two ligaments for the attachment of the pericardium to the diaphragm 

 is, perhaps, to keep it more fixed ; and, as there would be a vacuity 

 between them, nature has formed a lobe of the lungs to fill it up. 



The heart of quadrupeds is suspended in the middle between the 

 back and breast. The shape of the heart is generally owing to the 

 shape of the thorax. The flat chest has a flat heart, and the two 

 auricles are more parallel and similar [to one another], making often 

 two apices. The deep-chested animals, such as hares, dogs, horses, &c, 

 have more rounded hearts. The right ventricle almost surrounds the 

 left obliquely, and is not so low, so that it makes no part of the apex 

 [of the heart]. 



Thorax. — The upper part of the thorax in many quadrupeds is so 

 narrow from right to left as not to allow the common trunk of the left 

 subclavian to be longer than the right ; so that the superior vena cava 

 comes down nearly in the middle, just before the trachea. The vena 

 cava inferior is much longer in brutes than it is in the human subject ; 



