THE PROTEIN-BODIES. 297 



capable of being resorbed ; to this class belong not only the albu- 

 minous substances, but also their more or less remote derivatives, 

 as for instance, many gelatigenous substances, and likewise a num- 

 ber of less-known matters, as synaptase and diastase, the poison of 

 serpents, curarine, &c. Hitherto attention has naturally been for 

 the most part directed to the behaviour of the albuminous matters 

 in digestion. We have already, when treating of the function of 

 the gastric juice (in vol. ii, pp. 53-60), considered this subject 

 somewhat in detail. We there showed that the albuminous matters 

 are not merely dissolved by the gastric juice, but are likewise con- 

 verted into matters which, although similar in their elementary 

 composition to the substances from which they were derived, yet 

 differ essentially from them in their physical, and in several of their 

 chemical properties. We have proposed the term peptones for the 

 albumen, fibrin, casein, &c., after their metamorphosis by the 

 gastric juice, and we believe that it is these peptones which undergo 

 resorption in order to be again very soon converted in the lym- 

 phatics into the well-known coagulable albuminous matters. W r e 

 have been further taught by the experiments of Bidder and 

 Schmidt, that the gastric juice which is secreted is far from being 

 sufficient for the digestion of the protein-bodies necessary for nutri- 

 tion (see the notes to the section on " Gastric Juice, " in the 

 Appendix), and that the intestinal juice possesses in a high degree 

 the faculty of dissolving the protein-bodies, and thus preparing 

 them for being resorbed (vol. ii, p. 120). This metamorphosis of 

 the protein-bodies, and their subsequent resorption, should, how- 

 ever, be confined solely to the small intestine, which is the only 

 part of the intestinal tract in which true villi occur ; for if we 

 had no evidence from comparative anatomy that the caecum and 

 colon exerted only very little influence on the digestion of the 

 albuminates in carnivorous animals, the direct experiments which 

 have been recently instituted, partly by Steinhauser and partly by 

 myself, show that albumen and pieces of flesh when introduced 

 into fistulous openings in the lower part of the jejunum, or into 

 an artificial anus, pass off almost entirely unchanged by the rectum 

 (see note to "The Intestinal Juice," in the Appendix). 



We shall refer, under this fourth group of digestive objects, 

 almost solely to the protein-bodies and their immediate derivatives ; 

 it is, however, not improbable that many other substances which do 

 not possess the high physiological value of the albuminates, may 

 yet comport themselves during digestion in a very similar manner, 

 and we have already mentioned the gelatigenous tissues in con- 



