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A MANUAL OF VETERINARY PHYSIOLOGY 



nerve-fibre arises. These granules are intimately concerned in 

 the nutrition of the cell and its fibre, but whether as fluid or 

 granules is unknown. In a working cell the granules diminish, 



and under great muscular 

 exertion they may be re- 

 duced to fine particles, resem- 

 bling dust in appearance. 

 This is due to the chromo- 

 phile substance breaking up ; 

 the chromatolysis so produced 

 also occurs when the cell is 

 separated from its fibre. It 

 is evident from this that 

 nerve - cells, unlike nerve - 

 fibres, are capable of fatigue. 

 Nerve-cells are not all of the 

 same shape, size, or general 

 arrangement ; some have only 

 two processes growing from 

 the cell, and hence are called 

 ' bipolar cells '; other cells 

 have numerous processes, and 

 are called ' multipolar. ' All 

 the processes of a nerve are 

 not nerve-fibres ; of all the 

 processes in the multipolar 

 cell shown in Fig. 129 only one 



Fig. 127. — Structure of Multipolar 

 Cell (Barker). 



ah., Axon-hillock (the portion of the cell 

 from which the axon comes off), contain- 

 ing no Nissl bodies, and showing fibrilla- 

 tion ; ax, axis cylinder or axon ; m, 

 medullary sheath, outside of which is 



the neurilemma ; c, cell-substance (cyto- 

 plasm), showing Nissl bodies in a lighter is the beginning of a nerve 

 ground substance ; d, protoplasmic pro- fibre. It is called the axon 

 cesses or dendrites containing Nissl 

 bodies ; n, nerve-cell body or perikaryon ; 

 n', nucleolus ; nR., node of Ranvier ; 

 s.f., collateral fibril. 





Fig. 128. — Cell from the Nuclei of the Oculo-Motor Nerve of the 

 Cat (Barker, after Flatau). 



The nucleus, nucleolus, and Nissl bodies are shown on a larger scale 

 than in Fig. 127. 



it is the process of the cell which transmits the impulse. The 

 other processes are called dendrites ; they are the receiving portion 

 of the cell. The actual conducting materials in the cell are the 



