LIPIDS PRESENT IN BRAIN AND NERVOUS TISSUE 751 



exact mode of its formation is not understood. After being formed in the 

 brain, it is set free at the neuronal surface. It is closely associated with 

 the propagation of nerve impulses. The acetylcholine content in the 

 brain of man and dog, as well as in the peripheral nerves of the dog, is 

 given in Table 11. 



Table 11 



The Acetylcholine Content in the Brain of Dog and Man, 



and in the peripheral nerves of the dog° 



Man, Dog, 



Tissues /ig-/g- tissue Mg/g- tissue 



Peripheral nerves: 



Splanchnic — 10.5 



Vagosympathetic — 5.6 



Hypogastric — 4.0 



Sciatic — 2.5 



Brachial plexus — 2.3 



Optic chiasma — 1.0 



Central nervous system: 



Optic thalamus 0.85 1.7 



Cerebrum (gray) 0.75 0.9 



Corpus striatum 0.5 1.1 



Crus cerebri 0.5 1.1 



Spinal cord 0.45 0.75 



Cerebrum (white) 0.27 0.55 



Pons 0.20 0.5 



Medulla oblongata . 16 0.5 



Cerebellum 12 0.4 



a I. H. Page, Chemistry of the Brain, C. C Thomas, Springfield, 111., 1937, p. 71. 



The acetylcholine level in the central nervous system of the dog is about 

 double that in the central nervous system of man. However, a surpris- 

 ingly uniform parallelism obtains between the relative acetylcholine con- 

 tent of the several parts of the nervous system in the two species. In 

 only one instance (cerebellum, gray matter) does the descending order of 

 acetylcholine content fall out of line in the brains of the two species. 



Cholinesterase, which is the enzyme by which the level of acetylcholine 

 is regulated, occurs not only in the nerve endings but also in the brain. 

 This enzyme causes the destruction of the acetylcholine by catalyzing its 

 hydrolysis to acetic acid and choline. According to Ord and Thompson, 269 

 all areas of the human brain studied contained measurable amounts of this 

 enzyme, as judged by the hydrolysis of benzoylcholine and butyrylcholine. 



269 M. G. Ord and R. H. S. Thompson, Biochem. J., 50, xxxii-xxxiii (1952). 



