FIBROUS CONNECTIVE TISSUE. 69 



per cent. The soaking of gelatin in dilute acid, however, 

 results in the formation of a salt>-like compound, from which 

 the acid cannot be withdrawn by washing with water. By 

 adding a little ammonia to the water this may be accomplished. 

 From this short re'sum^ it is evident that pure gelatin from 

 white fibrous connective tissue is not widely different in 

 composition from commercial gelatin, so far as the content of 

 carbon, hydrogen, and nitrogen is concerned. In the content 

 of sulphur, however, there is a wide difference, pure gelatin 

 from tendons containing only 0.25 per cent of this element. 

 Especially important in this connection is the fact, now 

 brought out, that the sulphur-content of gelatin from white 

 fibrous connective tissue is very closely akin to that of the 

 related albuminoid elastin,* the latter, according to the latest 

 researches, containing 0.3 per cent of this element. Elastin, 

 however, differs widely from gelatin in its content of carbon 

 and nitrogen. Further, the fancied difference in the content 

 of sulphur between corneal gelatin and tendon gelatin also 

 falls away, although these bodies are plainly unlike in their 

 content of nitrogen. 



BEACTIONS OF GELATIN. 



Although the four samples of gelatin described were studied 

 with great care, no difference in chemical reactions was 

 observed. They all showed a very faint alkaline reaction and 

 were rather noticeably soluble in cold water. In trying pre- 

 cipitations with various reagents, a 2 per cent aqueous solution 

 of gelatin was made use of, and at room temperature this was 

 fluid enough for the purpose, but if warmed and allowed to 

 cool undisturbed the solution showed some tendency to 

 gelatinize. Halliburton f states that the power of gelatinizing 

 is possessed by solutions from 1 per cent up, but diminishes 

 with every successive solution. This somewhat weak power 



* Chittenden and Hart, Elastin and Elastose Bodies. Studies in Physiol. 

 Chem., Yale Univer., vol. iii, p. 19. Also Schwarz, Untersuchungen iiber die 

 chemische Beschaffenheit der elastischen Substanz der Aorta. Zeitschr. f. 

 physiol. Chem., Bd. xviii, p. 487. 



t Text-book of Chem. Physiol. and Pathol., p. 471. 



