THE TISSUES. 



27 



distinct from tlie protoplasm of the cartilage cells whicli lie in its 

 cavities; but as it is differentiated from the protoplasm, it must, 

 nevertheless, be regarded as a secreted product of the protoplasm— 

 a layer secreted by a cell : often an intercellular substance may be 

 seen in hyaline cartilage surrounding the cell like a capsule. This 

 was formerly regarded as a cell- 

 membrane belonging to the cell. 

 As these " capsules " can often 

 be shown to enclose groups of 

 cells consisting of several gene- 

 rations, which have resulted 

 from the fission of a siugle 

 cell, the enclosed cells were 

 looked upon as mother and 

 daughter cells, &c., and the 

 phgenomenonitself was regarded 

 as a case of endogenous cell- 

 formation. As a fact, these 

 " capsular systems " are merely 

 the expression of secretions, 

 not become homogeneous, and 

 formed by several generations 

 of cells which arose from one 

 another. The perfectly gradual 

 passage of cartilaginous tissue 

 in which such capsules may be 

 seen, into tissues where the intercellular substances is completely 

 homogeneous, shows that we have here to do with different stages 

 in the differentiation of one and the same secreted substance, which 

 has arisen in the former case by an interrupted, and in the latter 

 case by a regular, secreting activity of the cells. In virtue of the 

 anastomoses of the processes of cartilage-cells, cartilaginous tissue 

 comes very close to the next form of tissue, and it is only distin- 

 guished from it by the characters of its intercellular substance. 



Fig. 10. Cartilage from a Cephalopod. 

 a Simple, b Dividing cells, c Canaliculi. 

 d Aa empty cartilage capsule with, its 

 pores, e Transverse section of canaliculi 

 (after M. Fiirbringer). 



§ 23. 



5) Osseous tissue. This, the firmest form of the connective 

 substances, consists of an organic intercellular substance combined 

 with lime-salts, in which there are cells with fine anastomosing 

 processes; or it presents a ground-substance like that just men- 

 tioned, in which, however, there are no cells, but only cell-processes. 

 These processes traverse it as fine canaliculi. There are therefore 

 two structural phases of osseous tissue to be distinguished. 

 Cells enter into the composition of the one, but in the other they 

 simply send out fine processes into the pore-canals of its solid 

 ground-substance. 



The tissue containing bone-cells is the most common; it is 



