GENERAL ANATOMY OF THE TISSUES. 



sent nothing remarkable, and will be more particularly treated of in their 

 proper places in the special part. 



The chemical relations of connective tissues are well known : proper 

 connective substance when boiled yields common gelatine, and contains 

 besides a fluid, whose nature, on account of its generally minute quantity, 

 cannot be investigated. Only where it exists in considerable proportion, 

 as in the gelatinous connective tissue of embryos, can the presence of 

 much albumen and mucus be easily demonstrated in it. The chemical 

 qualities of the other constituents of the connective tissue will be spoken 

 of in their place. 



Connective tissue is of utility to the organism according to its compo- 

 sition, sometimes as a solid unyielding substance ; sometimes as a soft 

 support for vessels, nerves, and glands ; sometimes, finally, as a yielding 

 tissue, filling up spaces, and facilitating changes of position. Where 

 elastic elements are present in it in great quantities, its nature alters; 

 and a great abundance of fat or cartilage cells gives it an unusual soft- 

 ness or resistance. The connective tissue is invariably developed from 

 cells, and, in fact, from fusiform or stellate vesicles, which become 

 united into long fibres or networks, and often break up into fibrils before 

 their union. The mode in which this takes place is not yet quite made 



out, but it is most proba- 



Fig. 30. 



ble that the cells, as they 

 elongate, change with 

 their membrane and con- 

 tents, into a homogeneous 

 softish mass, which sub- 

 sequently breaks up into 

 a bundle of fine fibrils 

 and some intermediate 

 substance. The develop- 

 ment of the homogeneous 

 connective tissue has as 

 yet been little investiga- 

 ted, but it would seem, 

 like the other, to proceed 

 from a fusion of rounded 

 or elongated cells, which 

 are perhaps united by an intermediate substance, in which the meta- 

 morphic process has only gone so far as the development of a homoge- 

 neous mass, but has not attained the stage of fibrillation. The bundles 



FiG. 29. Formative cells of the connective tissues from the skin of the trunk in a sheep's 

 embryo, 7 lines long : a, cell without any indication of fibrils 5 6, with commencing ; c, with 

 distinct fibrils. Magnified 350 diameters. 



FIG. 30. Three formative cells of the areolated connective tissue from the allantois of a 

 sheep's embryo, 7 lines long. Magnified 350 diameters. 



