128 FIBRE-CELLS, ETC. 



or to the minimum of cytoblastema between the epithelium - 

 cells : or, lastly, to the fluid, in which the cells of the first 

 class are formed. In this way one can also readily understand 

 how fibro-cartilage forms a gradual transition between true 

 cartilage and fibrous tissue ; it only requires that the cartilage- 

 cells pass through the same transformations as the elementary 

 cells of areolar tissue. 



As the present class was based upon the alteration in form 

 which the cells comprised in it undergo, it necessarily could not 

 present many modifications in the shape of the cells, and accord- 

 ingly exhibits throughout merely an elongation of nucleated 

 cells into fasciculi of fibres, and a subsequent splitting of the 

 bodies into fibres. We have already seen the types of these 

 changes in the second class, where the pigment-cells and those of 

 the crystalline lens, &c, became elongated by a more vigorous 

 growth of the cell-membrane at different spots ; and the class 

 now before us merely affords us an instance of the same pro- 

 cess in a higher degree, since here, one side of one of these 

 more highly developed fibre-cells gives origin to a great num- 

 ber, or even a whole fasciculus, of fibres. The cells of the 

 cortex of the feather also furnished us with an example in the 

 same class of the division of the body of the cells into fibres. 

 Inasmuch as the prolongations of the pigment-cells remain 

 hollow, however minutely they may ramify, one may suppose the 

 same to be the case Avith regard to the fibres of the tissues 

 now under consideration. The decision of this point would, 

 as we shall subsequently see, be of great importance for 

 the theory of nutrition; but it is quite impossible to deter- 

 mine it by observation, in consequence of the cells of this class 

 not possessing any characteristic contents like those of pigment. 

 An observation by Purkinje and Raiischel was quoted, however, 

 in favour of these cells being hollow. If the hollowness of the 

 fibres of areolar tissue, &c, could be proved, there would 

 then be a division of a single cell into many cells at each 

 transformation of a fibre-cell, and thus the fibrous tissues would 

 not lose their cellular character. 



The fibre- cells undergo chemical changes during their 

 growth and gradual transformation into the fibres of areolar 

 tissue, since that tissue, when boiled, even long after the forma- 

 tion of fibres has commenced, yields no gelatinizing gelatine. 



