CHAPTER VIII. 



TISSUES OF THE CONNECTIVE SUBSTANCE. 

 I. The Connective Tissues. 



THE form-elements of the typical connective tissues are cells of 

 various kinds, of a not very well known chemical composition, and 

 gelatine-yielding fibrils. Besides these, elastic formations are often 

 found in variable amounts, though sometimes in such predominant 

 quantities that the connective tissue passes nearly into an elastic 

 tissue. Mucin is also found in the connective tissue, serum 

 globulin and serum albumin occurring in the parenchymatous fluid 



(LOEBISCH). 



If finely-divided tendons are extracted in cold water, the albu- 

 minous bodies soluble in the nutritive fluid in addition to a little 

 mncin are dissolved. If the residue is extracted with half-satu- 

 rated lime-water, then the mucin is dissolved (ROLLETT, LOEBISCH) 

 and may be precipitated from the filtered extract by saturating 

 with acetic acid. The digested residue contains the fibrils of the 

 connective tissue together with the cells and the elastic substance. 



The fibrils of the connective-tissue consist of collagen. They 

 are elastic, swell slightly in water, somewhat more in diluted 

 alkalies or acetic acid, but on the other hand are shrivelled by 

 the action of certain metallic salts, such as ferrous sulphate or 

 mercuric chloride, and by the action of tannic acid, which forms 

 with collagen an insoluble combination. Among these combina- 

 tions, which prevent the putrefaction of collagen, that with tannic 

 acid has been found of great value in the preparation of leather. 

 In regard to tendon mucin see page 32, and in regard to collagen, 

 glutin, and elastin see pages 36-38. 



