DESCRIPTION. 27 



motion, proportion and gravitation; just as the astronomers are 

 indebted to the distance of their view, and the superficiality of their 

 objects. Good science then, we repeat, will not refuse to attend 

 upon anatomical plates, though not the science of the surgeon. 



The brain is an oval mass, filling and fitting the interior of the 

 skull, and consisting of two substances, a gray, ash-colored or cine- 

 ritious portion, and a white, fibrous or medullary portion. These 

 substances occupy different positions in different parts of the brain. 

 The gray portion constitutes the circumference of the large and 

 front division which is called the cerebrum ; it also enters into the 

 interior of the same in various parts, and forms both the centre and 

 circumference of the cerebellum and the centre of the spinal mar- 

 row. The white portion makes up the greater share of the brain. 

 Besides these divisions of substance the brain also presents divisions 

 of form. It is parted into two great masses, viz., the cerebrum and 

 cerebellum, and at its base there are two other portions, named the 

 annular protuberance and medulla oblongata. These are the four 

 primary divisions on the surface of the organ. The spinal marrow, 

 which runs down through the vertebrae or back bones, is the con- 

 tinuation of the medulla oblongata. The above parts collectively 

 are the bed and trunk of what is called the nervous system. From 

 all those already mentioned there arise certain white cords, the 

 nerves, which come out through holes in the skull, and through 

 notches between the back bones, and run to all parts of the body, 

 gradually splitting into filaments, which at length become invisible 

 by reason of their fineness. There are generally reckoned to be 

 eleven pairs of nerves arising from the brain, and thirty-one pairs 

 from the spinal marrow. Besides this great nervous plant which 

 continues the life of the head and its appendages, there is also 

 another proper to the body, as it were a creeping or parasitical 

 system, which weaves its meshes among the branches of the former : 

 this is the system of the sympathetic nerves. It is not obviously 

 referable to a centre, like the system just described, but it' has 

 many small centres scattered throughout the body, but especially 

 near the important organs, the heart, the stomach, &c. These cen- 

 tres are called ganglions, and are said to consist principally of gray 

 matter. Innumerable fine nerves radiate from them to the viscera, 



