l8l6 HANDBOOK OF PHYSIOLOGY ^NEUROPHYSIOLOGY III 



table I . Activity of Respiratory Enzyme Systems in Various Cell Types of Mammalian Xervous System* f 



* See text for references. 



t Activity is expressed in mmole of substrate utilized per gm dry \vt. per hr. at 37 °C. 



I pinole O l . utilized per mg dry wt. per hr. 



§ /imolc COj liberated per mg dry wt. per hr. 



vessels are generally absent from the central nervous 

 system in invertebrates (50). Electronmicroscopy has 

 revealed the existence of fine granules (0. 1 to 0.5 ju) 

 within neuroglia which occasionally are found in 

 large clusters as if they were in the process of being 

 discharged into the intracellular space (103). The 

 nerve cell bodies of the invertebrate nervous system 

 also appear to contain secretory-like inclusions of 

 varying sizes in close association with the 'Golgi' 

 complex or a double-lavered endoplasmic reticulum 

 -■1 



OYTOCIIKMISTRY 



With the development of histochemical and refined 

 microchemical techniques, a considerable amount of 

 information has accumulated on the localization of 

 enzymes and other chemical substances within the 

 neuron as well as on the differentiation of neuronal 

 chemistry from the complex interrelationship of the 



nonneuronal elements. Although histological evidence 

 is scanty, it appears as though most of the gray 

 matter of the brain is comprised of dendritic processes 

 and that the perikarya and glia comprise less than 

 10 per cent of the total mass (115). In most 

 mammalian species an estimate of 5 per cent for the 

 total mass of nerve cell bodies in whole brain would 

 be somewhat high (115). 



By means of ultramicrochemical techniques ii lias 

 been possible to study the metabolism of distinct 

 types of cell populations in the hippocampal and 

 cerebral cortex of rabbit brain (78, 92, 106, 110). 

 (S,-c table i.) Such enzymes as the dehydrogenases 

 (no) and cytochrome oxidase (qj, o;' seem to be 

 richest in the lasers containing pyramidal cell bodies 

 and dendritic processes, while aldolase and adenosine- 

 triphosphatase have a more random distribution 

 throughout the cortex. In many regions of the brain 

 stub as the cerebral and cerebellar cortex there is 

 some justification, therefore, for believing that 



