CHAPTER XIX. 



THE SUPPOETING TISSUES 



IN contradistinction to those tissues of the animal body which are 

 essentially composed of cells, and in which the albumins proper con- 

 stitute the greater portion of the organic solids, we find that in the 

 so-called supporting tissues which comprise the common connective 

 tissues, cartilage, and bone, the albuminoids stand in the foreground. 

 Their preponderance here coincides with the extensive development 

 of the matrix, while the cellular elements enter into the histological 

 picture to a more or less insignificant extent. This statement, how- 

 ever, holds good only for the higher animals, and more specifically 

 for the fully developed animals. In lower forms of life, and during 

 the embryonic stage of the development of the higher forms, these 

 structures are rich in cells, and we find then an underlying matrix 

 in which a differentiation into supporting tissue proper has not as 

 yet occurred or exists to only a limited extent. Such tissue is 

 termed embryonic connective tissue, and is also known as mucous 

 tissue. In the adult animal it is found only in the vitreous humor 

 of the eye. In typical form it is seen in the umbilical cord, in 

 which it constitutes the so-called jelly of Wharton. The matrix is 

 here very rich in water, and contains a mucinous substance, which 

 is soluble in a 0.5 pro mille solution of hydrochloric acid. In addi- 

 tion, traces of albumin are met with, while collagen is usually absent. 

 Of the composition of the cells nothing specific is known, but it is 

 quite likely that their processes consist of collagen. 



White Fibrous Tissue. The fibrils of white fibrous tissue con- 

 sist of collagen, and are bound together by a cement-substance, 

 which represents the original undifferentiated matrix. As in the 

 case of the embryonic connective tissue, this contains traces of the 

 common albumins of the plasma, and a mucinous substance, which, 

 in contradistinction to that of the umbilical cord, is insoluble in 

 a 0.5 pro mille solution of hydrochloric acid. Analysis of this 

 substance has given the following results : C, 48.30; H, 6.44; N, 

 11.75 ; S, 0.81 ; and O, 32.70 per cent. According to Lobisch, its 

 formula is C 160 H 256 N 32 SO 80 . To isolate the body in question, liga- 

 ments, such as the tendo Achillis, are cut into small pieces and 

 first extracted with cold water, which dissolves the albumins and 

 a small fraction of the mucin. The remaining material is then 

 placed in a half-saturated solution of lime-water, in which the 

 mucin is readily soluble. After filtering, the substance is precipitated 

 by adding an excess of acetic acid (see page 124). The residual sub- 

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