130 MUSCLE. 



the cell-walls then become blended, in such manner that 

 merely simple septa remain, dividing each succeeding cell-cavity 

 from its neighbour. These septa, however, become absorbed, 

 so that the cavities of the different cells communicate. Instead 

 of a number of primary cells, we then have one single long 

 one, which we shall call a secondary cell. The cavity of such 

 a one, therefore, consists of the united cavities of the original 

 cells, and its cell-membrane of all their blended cell-mem- 

 branes, except that the parts with which they were in contact 

 are absorbed. The growth of the secondary cell proceeds 

 like that of any simple independent cell. This appears to 

 be the process of formation in muscle and nerve, so far, at 

 least, as the observations, which will presently be communi- 

 cated, extend. When the primary cells have a stellate figure, 

 their bodies are not applied in rows, as in nerve and muscle, 

 but are generated in larger interspaces filled with cytoblas- 

 tenia or with cells of another kind. Their prolongations, 

 however, come in contact, the walls coalesce at the points 

 of junction, and the blended septa then become absorbed, so 

 that the cell-cavities, which were at first separated, now com- 

 municate. In this manner, when several prolongations of 

 one cell come into contact with those of another, or of several 

 others, we obcain, in the place of isolated, hollow, stellate cells, 

 a network of canals, which are, in the first instance, somewhat 

 thicker at the parts corresponding to the bodies of the cells, 

 but become of pretty equal dimensions, in consequence of 

 more vigorous expansion of the communicating prolongations. 

 This appears to be the mode in which the capillary vessels are 

 formed. The following detailed statement of observations 

 upon the relation which muscles, nerves, and capillary vessels 

 bear to elementary cells, will show how far the description 

 just given, as the probable mode of formation, is to be regarded 

 as proved by these, as yet, very incomplete researches, and will 

 also indicate what deficiencies have yet to be supplied. 



1. Muscle. To ascertain the relation which this tissue 

 bears to the elementary cells, we must have recourse to the 

 history of its development. I was, unfortunately, prevented 

 from investigating the earliest formation of muscular fibre, in 

 consequence of not being able to obtain any very young 



