ELEMENTS OF STKUCTUKE. 



99 



of connective tissue presents for our consideration is not less consider- 

 able than that existing among the cells themselves. 

 Consisting originally of albuminous matters (con- 

 sistently with its origin from the protoplasm of 

 the cells), it commences later on, as its solidity 

 increases, to contain glutin, or more properly, 

 collagen. In bone again, and in dentine, it 

 attains a high degree of hardness and firmness by 

 the reception into its' composition of large quan- 

 tities of the salts of lime. 



It is not, however, changes alone of this kind 

 in consistence and composition which are to be 

 met with in the intercellular substance of the 

 connective-tissue group. Even if it escape solidi- 

 fications of the species just described, it still 

 manifests a great tendency to become streaky or 

 banded, or finally to break up into fibrillae. 

 Again, between all these varieties no very distinct 

 boundaries exist; and in the neighbourhood of 

 banded or fibrillated portions, we may encounter 

 more or less of a residue, as it were, of unchanged 

 homogenous intercellular substance. The fibrillse 

 alluded to are sometimes found in the form of 

 extremely fine isolated threads, but are usually 

 Arranged in bundles. They are known as con- 

 nective or cellular-tissue fibrillse. 



Fig. 104 is designed to represent the latter. 

 In the preparation, which is from a structure four months, 

 intermediate between true cartilaginous and connective tissue, we find 

 simple cartilage cells scattered among bundles of fibres. In fig. 105 

 also we have these fibres (/), (grouped 

 in bundles at (g] ), between stellate con- 

 nective-tissue cells (a-e). 



But this metamorphosis of the for- 

 merly homogenous intercellular mass 

 into collagenic fibres is not the only 

 one met with in connective tissue. 

 Another kind of thread-like element, 

 consisting of a material with far greater 

 power of resistance to reagents (comp. 

 15), is formed by the transformation 

 of intercellular matter, and is known as 



the elastic fibre (fig. 105, h). It also Fig. 104.- Fibrous cartilaginous substance 

 .. , , , , ' ' , from a ligamentum intervertebrale of man 



is liable to vary much, both as regards 



strength and the occurrence or absence of branches (fig. 106), 



However, this appearance of elastic matter in the form of fibres is not 

 the only one it makes in connective tissue. The intercellular matter 

 may be transformed, at the boundaries of the tissues in question, towards 

 the cells and cellular networks, and likewise at their surfaces, &c. (but 

 still retaining its homogenous appearance), into limiting layers of divers 

 kinds, formed of a substance identical with, or optically and chemically 

 the same as elastin. These have frequently been erroneously taken for 

 cell-membranes and other peculiar envelopes. 



Thus in the course of development of connective substance, a whole 



