58 THE HUMAN BRAIN. 



centuries. But their monuments are the living parts of their science. 

 And we must be content with alleging, that these men, with no ex- 

 ception, believed in the animal spirits, and the tubular construction 

 of the nerves; which, as the illustrious Glisson, our countryman, 

 remarks, was in his time " accredited by nearly all physicians ; and 

 by all philosophers." 



We now therefore assume that the nerves are tubes, and that 

 there is a special fluid, cerebral, spinal, sympathetic, i. e., following 

 in its degrees and divisions the solid pieces of its nervous frame : 

 and the question occurs, Where is this fluid engendered? We 

 reply, that its matrix everywhere is the cineritious substance; 

 that as the vehicle of what comes down from above, it begins every- 

 where with the beginning of the bodily order, which lies in the 

 cineritious spheres. The latter show luxuriant provision for the 

 purpose in the arterial meshes which supply them. But to pursue 

 this subject would require a treatise on the life of the blood. We 

 shall, however, recur to it in the sequel. 



But another question presents itself — Is there a circulation of this 

 living fluid? Do its centres impel it, as the heart propels the blood? 

 Is there a cerebral force or a motion of the nervous system ? Or is 

 the brain, besides being solid and exclusive, also stationary and 

 paralytic? Or on the other hand, if there be any natural force in 

 brains, what is it? 



First for the facts. Two motions are already admitted to have 

 place in the head, one corresponding to the beating of the arte- 

 ries or heart; the other, to the breathing of the lungs. By laying 

 the fingers upon the open fontanelle of a young infant, the reader 

 will feel the first-named motion. It is the stroke of the heart com- 

 municated to the arteries of the dura mater. This is no cerebral 

 force, or proper motion of the brain. As for the second or lung 

 movement, it occurs as follows. When the lungs expand to draw 

 in the air, a tendency to vacuum is created in the chest, which 

 causes the fluids all over the body to rush or to incline thither, to 

 fill the threatened void. In short the lungs, besides breathing in the 

 air, quaff" down the venous blood from the brain, and suck up that 

 from the body. The consequence is, that in inspiration the skull is 

 more empty of blood than at other times. Hence when the 



