144 CONNECTIVE TISSUE. 



cavities, while Virchow asserted that the intercellular substance 

 contains " cells/' the seats of life. Between 1860 and 1870, his- 

 tologists began to be aware that the intercellular substance 

 contains cavities, in which the cells are imbedded. Virchow^ 

 in 1851, was also the first to recognize that all varieties of connect- 

 ive tissue belong to one group, for the designation of which he 

 proposed the rather unsatisfying term " connective substances." 



As A. Rollett * says : " The connective tissues are developed from "the 

 middle germinal layer, in which blood and muscle also originate. The typical 

 connective substances are recognized histologically by the circumstance 

 that they contain extensive and continuous layers of material (intercellular 

 substance), which, when compared with the cellular structures distributed 

 through its substance (protoplasma), or the morphological elements in other 

 tissues, always appears as a more passive substance and one which participates 

 but slightly in the processes characteristic of life. These masses consist, for 

 the most part, of gelatine -forming substances, such as collagen, chondrogen, 

 and ossein. The connective tissues frequently pass by substitution or genetic 

 succession into one another; they appear, therefore, to be morphologically 

 equivalent, so that in many instances certain organs, or parts of organs, 

 belonging to animals nearly allied to one another, are formed sometimes of 

 one, sometimes of another, of these tissues." 



The basis-substance, the hitherto called intercellular substance, 

 is a product of the lifeless bioplasson liquid which, probably 

 nitrogenous from the very beginning, is transformed by chemical 

 changes into the nitrogenous, more or less solid, mass termed 

 basis-substance. In the same variety of connective tissue, espe- 

 cially in the fibrous, the basis-substance may exhibit different 

 degrees of solidification. Bundles of fibrous connective tissue are r 

 f. i., built up of striated, glue-yielding basis-substance; the 

 bundles are separated from each other by the less solid cement-sub- 

 stance ; and they are bounded, both at their peripheries and around 

 the plastids, by a more solid, dense, and chemically indifferent 

 elastic substance. The so-called elastic fibers are but a variety 

 of the glue-yielding basis-substance, in a high degree of solidi- 

 fication. 



According to the nature of the interstitial substance, the 

 morphological properties of which are far better known than the 

 chemical, we may distinguish four varieties : 



Myxomatous or mucoid basis-substance, a jelly-like, translucent 

 substance, not yielding gelatine ; 



* "A Manual of Histology," by S. Strieker. American translation edited by Albert H. 

 Buck, 1872. Chapter: "The Connective Tissues." 



