. 



CHAP. VII.] THE CONNECTIVE TISSUES. 255 



Products of a . Action of boiling water. When solutions of 



Wonof P geia- gelatin are subjected to the action of boiling water for 

 tin. a longer period than 25 hours they lose the property of 



gelatinizing, and are found to contain a mixture of two peptone-like 

 bodies, to which Hofmeister has given the name of Semiglutin and 

 Hemicollin. 



Semiglutin is very little soluble, whereas hemicollin is soluble, in 

 70 80 per cent, alcohol. 



The former substance is precipitated by platinum tetrachloride, 

 the latter is not. Both bodies furnish glycine and leucine when 

 treated with boiling hydrochloric acid and stannous chloride. To semi- 

 glutin Hofmeister ascribes the formula C 55 H 8 gN 17 O 22 and to hemicollin 

 C 47 H 70 N 14 19 . In the process of decomposition into these bodies collagen 

 takes up water, increasing 2'22 per cent, in weight. The following 

 equation exhibits the relationship of these bodies, according to 

 Hofmeister, 



C,JW> S + 3H 2 = CJIssN.A, + C^HJS.A, 



Collagen Semiglutin Hemicollin 



b. Action of boiling sulphuric acid. When subjected to the 

 action of boiling sulphuric acid, collagen and gelatin yield, amongst 

 other products, ammonia, leucine, glycine, and, perhaps, aspartic 

 acid. 



c. Action of caustic baryta in heated sealed tubes. When 

 heated with solution of caustic baryta in sealed tubes, ammonia, 

 carbon dioxide, acetic and oxalic acids, and a mixture of amido-acids 

 (containing glycine and alanine, amido-butyric acid, traces of glutamine, 

 &c.) are obtained. 



d. Action of pancreatic ferments. When subjected to the com- 

 bined action of the pancreatic ferment and putrefaction gelatin yields 

 gelatin-peptones, leucine, glycine, volatile fatty acids, ammonia and 

 carbon dioxide. Amongst the fatty acids are acetic, butyric and 

 valerianic acids (Nencki 1 ). 



The Elastic Fibres of Connective Tissue. Elastiri. 



When ordinary connective tissue is treated with acetic acid, the 

 white fibres swell up and become transparent, whilst the elastic fibres 

 remain unaltered and are therefore very distinctly seen. When the 

 same connective tissue is subjected to prolonged boiling in water, the 

 collagen of the white fibres undergoes solution and there is left a 

 network of elastic fibres. These fibres are composed of an elastic 

 substance which offers remarkable resistance to the action of 

 chemical reagents, and to which the term Elastin has been applied. 



1 Nencki : Ueber die Zersetzung der Gelatine und des Eiweisses bei der Fdulniss mit 

 Pancreas. Barn, 1876. Abstracted in Maly's Jahresbericht, Vol. vi., p. 31. 



