CONNECTIVE TISSUES. 545 



The fibrils of the connective tissue are elastic and swell slightly in 

 water, somewhat more in dilute alkalies or in acetic acid. On the other 

 hand, they shrink by the action of certain metallic salts, such as ferrous 

 sulphate or mercuric chloride, and tannic acid, which form insoluble 

 compounds with the collagen. Among these compounds, which prevent 

 putrefaction of the collagen, that with tannic acid has been found of 

 the greatest technical importance in the preparation of leather. In 

 regard to the collagens, gelatins, elastins, and reticulins, see pages 116 

 to 121. 



The tissues described under the names mucous or gelatinous tissues 

 are characterized more by their physical than by their chemical prop- 

 erties, and have been but little studied. This much, however, is 

 known, that the mucous or gelatinous tissues contain, at least in certain 

 cases, as in the Acalephse, no mucin. 



The umbilical cord is the most accessible material for the investiga- 

 tion of the chemical constituents of the gelatinous tissues. The mucin 

 occurring therein yields, according to VAN LIER, an ethereal sulphuric 

 acid (glucothionic acid) like the tendon mucoid. C. TH. MORNER 1 

 has found a mucoid in the vitreous humor which contains 12.27 per 

 cent nitrogen and 1.19 per cent sulphur. 



Young connective tissue is richer in mucoid than old. HALLIBURTON 2 

 found an average of 7.66 p. m. mucoid in the skin of very young children 

 and only 3.85 p. m. in the skin of adults. In so-called myxcedema, 

 in which a re-formation of the connective tissue of the skin takes place, 

 the quantity of mucoid is also increased. 



' The connective tissue and also the elastic tissue are richer in water 

 and poorer in solids in young animals as compared with full-grown 

 animals. This may be seen from the following analyses of the Achilles 

 tendon (BUERGER and GIES) and of the ligamentum nuchse (VANDE- 

 GRIFT and GiES 3 ): 



Achilles tendon. Ligament/ 



1 Zeitschr. f. physiol. Chem., 18, 250. 



2 Mucin in Myxcedema: Further Analyses. King's College Collected Papers 

 No. 1, 1893. 



'Buerger and Gies, Amer. Journ. of Physiol., 6; Vandegrift and Gies, ibid, 5. 



