668 



A MANUAL OF PHYSIOLOGY 



work. The neuron, in fact, lives by its function, or, in common 

 language, by doing its work. 



Chromatolysis may also be produced in nerve-cells in extensive 

 superficial burns, in tetanus caused by the injection of bacterial 

 cultures, in acute alcoholic poisoning, and in other ways. In several 

 kinds of intoxication for example, chronic alcoholism Berkley 

 observed, in preparations impregnated with silver nitrate according 

 to the method of Golgi, that the earliest changes were the disappear- 

 ance of the gemmules of the dendrites. It is probable that neither 

 the chromatolysis nor the loss of the gemmules should be looked 

 upon as the token of any specific lesion ; they are simply signs that 

 the normal action of the neuron has been deranged. 



Grey and WMte Matter. Nerve- cells are the most distinctive 

 histological feature of the grey nervous substance. Sown thickly 

 in the cerebral cortex, the basal ganglia, the floor of the fourth 

 ventricle, and the cervical and lumbar enlargements of the cord, they 



FIG. 235. ChLLS FROM THE NUCLEI OF THE OCULOMOTOR NERVES OF THE 

 CAT THIRTEEN DAYS AFTER DIVISION OF THE ROOT FIBRES ON ONE 

 SIDE (BARKER, AFTER FLATAU). (NISSL'S STAIN.) 



a, normal cell from side on which the roots were not cut ; b, cell from side operated 

 upon. Only a few Nissl bodies are present in b, and the nucleus is displaced to one 

 side of the cell. 



are scattered more sparingly wherever the grey matter extends. They 

 also occur in the spinal ganglia and their cerebral homologues (such 

 as the Gasserian ganglion), in the ganglia of the sympathetic system 

 and the sporadic ganglia in general. But wide as is their distribution 

 and great as is the size of the individual cells, some of which have a 

 diameter of 140 /x, or even more, they yet make up but a small 

 portion of the whole of the central nervous substance, the total 

 weight of the 9,000 millions of nerve-cell bodies in the human brain 

 being less than 27 grammes (Donaldson). And although it is not 

 to be wondered at that objects so notable when viewed under the 

 microscope should have struck the imagination of physiologists, it is 



