FUNCTIONS OF QUADRUPEDS. 3 



and their general organs of sense, have the same essential 

 parts. They have all an alimentary canal, a liver, a pan- 

 creas, a spleen, and kidneys. In short, their general structure 

 is so nearly allied, that it is difficult to determine whether, 

 on the whole, the resemblances or the differences are to be 

 considered most predominant. These surely are so many 

 satisfactory demonstrations that " no disposition of matter 

 can give mind ; and that the body, how nicely soever it 

 may be formed, is formed in vain, when there is not infused 

 a soul to direct its operations." 



The Organs of Motion. 



The bones, (or skeleton,) constitute the frame-work of 

 the bodies both of men and quadrupeds. They surround 

 the cavities, defending the parts which ar6 of greatest im- 

 portance in the animal economy, such as the brain, and the 

 heart; and they serve as levers on which the muscles act. 

 They are covered, externally, with a membrane composed 

 of nerves and vessels, denominated 'periosteum ; and the 

 cavities of all the long bones contain a peculiar kind of 

 fatty substance called marrow. They are joined together 

 either, as in the skull, by sutures, where the edges of two 

 flat bones are denticulated into, touch, or lie upon each 

 other ; by being wedged one into another, as the teeth into 

 the sockets of the jaws; or by ligaments, a tough and 

 strong arrangement of fibres, which alone allow of free 

 motion to the members. In the articulations of the im- 

 movable bones, the periosteum is continued from one bone 

 to the other, and is more intimately connected at the place 

 of their junction, than to any other part. On the contrary, 

 in the movable articulations, the 'opposite surfaces of the 

 bones are free and distinct : each is coveted with a smooth 

 and polished cartilage, and the interval is occupied by a 



B 2 mucilaginous 



