x] of the Nervous System. 2ol 



" From the air which has thus made its way into the brain, 

 " and from the vital spirit which on account of the numerous 

 "flexures becomes more and more fitted for the use of the 

 "brain, the animal spirit is by the special power of the brain 

 " elaborated in the right and left ventricles, and in the cavity 

 " common to the two known as the third ventricle. A portion 

 "(of this animal spirit) is carried from this third ventricle, 

 "directed through the oblong channel (aqueduct of Sylvius) 

 "between the bodies which resemble the nates and testes to 

 " the ventricle of the cerebellum (fourth ventricle) which is 

 "formed by the sinus of the cerebellum, and partly by the 

 " cavity of the beginning of the dorsal medulla (spinal cord). 



11 From this ventricle no mean portion of the animal spirit 

 "is directed into the dorsal medulla and into the nerves 

 " springing from it. From the other ventricles of the brain 

 " however the spirit is carried into the nerves springing directly 

 "from them, and so to the organs of the senses and voluntary 

 " movement. 



" Meanwhile, we will not too anxiously discuss whether the 

 " spirit is carried along certain hollow channels of the nerves, as 

 " the vital spirit is carried by the arteries, or whether it passes 

 " through the solid material of the nerves, as light passes 

 " through the air. But in any case it is through the nerves 

 " that the influence of the brain is brought to bear on any part, 

 " so far I can certainly follow out the functions of the brain by 

 " means of vivisections, with great probability and indeed truth." 



In his chapter on vivisections, he shews how by cutting or 

 ligaturing this or that nerve you can abolish the action of this 

 or that muscle, or how having ligatured a number of nerves, 

 by loosing now this and now that ligature, you can bring this 

 and that muscle into action again, all shewing that the con- 

 traction of the muscle is dependent on its nerve. He mentions 

 incidentally that you may divide a muscle lengthwise without 

 stopping its contraction, but if you cut it crosswise, you do 

 interfere in proportion to the depth of the cut. He shews that 

 it is the nerve itself which is the essential agent, and not its 

 membranes, for you may remove the membranes without inter- 

 fering with movement. He further shews that if you lay bare 



F. L. 17 



