CHAP. II.] DIGESTION OF COLLAGEN AND GELATIN. 145 



have a close genetic relationship to the albuminous bodies proper, 

 and which are, therefore, often ( referred to as albuminoid bodies; 

 these are collagen and gelatin, chondrin (?), mucin, elastin, keratin, 

 We have now to examine the action of peptic digestion upon these 

 bodies. 



1. Digestion of Collagen and Gelatin. 



By the action of pepsin and dilute hydrochloric acid, collagen 

 (as in connective tissue and in bone) is converted into gelatin more 

 rapidly than is the case when it is merely subjected to the action 

 of dilute acids. Gelatin is acted upon by pepsin and hydrochloric 

 acid. It slowly loses the property of separating from its solutions 

 in the form of a jelly, and its specific laevo-rotatory power slightly 

 diminishes 1 . 



According to Etzinger 2 the artificial digestion must be continued for 

 48 hours in order to deprive gelatin of the property of gelatinizing. 



Uffelmann 3 , however, observed that in the stomach of a boy with gastric 

 fistula gelatin was so altered in the course of an hour as to be deprived of 

 the power of gelatinizing, whilst he found that with artificial gastric juice 

 digestion had to be continued for from 18 to 24 hours to produce the same 

 effect. 



As the ultimate product of the action of pepsin and hydrochloric 

 acid on gelatin, there is produced a gelatin-peptone, or perhaps 

 gelatin-peptones, which have yet to be subjected to thorough in- 

 vestigation. According to Tatarinoff, gelatin-peptone has an acid 

 reaction, decomposes carbonates, and forms compounds with the 

 alkaline earths, which have an alkaline reaction. Its solutions are 

 said not to differ materially in their chemical reactions from solutions 

 of gelatin 4 . 



2. Digestion of Chondrigen and Chondrin 5 . 



Chondrigen and chondrin are dissolved 'and digested somewhat 

 more slowly than collagen and gelatin, with the formation first of 

 acid-albumin, and then of peptone, in addition to a body which 

 reduces cupric oxide in alkaline solution 6 . 



1 J. de Bary, ' Untersuchungen iiber Leimstofife.' Hoppe-Seyler's Untersuchungen, 

 Heft i. (1866), p. 75. 



2 'Etzinger, 'Ueber die Verdaulichkeit der leimgebenden Gewebe.' Zeitschr. f. 

 Biol., Vol. x. p. 84. 



3 Uffelmann, 'Untersuchungen an einem gastrotomirten fiebernden Knaben.' 

 Archiv f. klin. MecL, Vol. xx. p. 535. 



* Tatarinoff, ' Zur Kenntniss der Glutinverdauung.' Centralblatt f. d. med. Wissen- 

 schaft (1877, No. 16). Maly's Jahreslericht, Vol. vn. p. 277. 



5 " The information given under this head is obtained entirely from Hoppe-Seyler, 

 Physiolog. Chemie, p. 234. 



6 See Vol. i. p. 270, ' Products of Decomposition of Chondrin.' 



G. 10 



