THE CELL-DOCTRINE OF PHYSIOLOGY. 133 



At other times the cells are elongated and fusiform, as in 

 woody fibre ; or they may send forth prolongations, assuming 

 a stellate or irregular appearance, as in the pigment cells of 

 the Batrachia, and Fishes, or some of the vesicles in the gray 

 matter of the nervous system. Further, the original bounda- 

 ries of the cells may be altogether lost, from their coalescence 

 with each other ; or their cavities be so occupied by internal 

 deposits that they may be mistaken for solid fibres. 



The nuclei are also subject to change of form. In some 

 instances we find it sending out radiating prolongations, so that 

 it assumes a stellate form, like that of the cells of the Gera- 



Fig. 40. 



nium-petal, Fig. 40 ; this seems also to be the case with the 

 nuclei of the bone cells. In vegetables, the wall of the cell 

 always remains, while in bone it disappears, and ithe canaliculi 

 anastomose. In other cases it seems to resolve itself into a 

 fasciculus of fibres ; and this Henle conceives to be the origin 

 of the yellow fibrous tissue. Further, it may separate into a 

 number of distinct fibres, each composed of a linear aggre- 

 gation of granules; in this manner, the dental tubuli appear 



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