402 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



such tubes, but could not get it to act outside the body. Similar ex- 

 periments were carried out by Stevens 1 of Edinburgh, who availed him- 

 self of the services of a juggler possessing a trick of swallowing stones 

 and regurgitating them. This man he gave to swallow some hollow 

 silver balls which were perforated with holes ; the balls were screwed 

 together in two halves and could be filled with meat. He found that 

 the meat was rapidly dissolved and disappeared. To Stevens also belongs 

 the credit of being the first to observe digestion outside the body. He 

 obtained gastric juice from a dog's stomach, and found that when a piece 

 of meat was subjected to its action in a warm place it became dissolved 

 in about eight hours. 



Soon afterwards Spallanzani confirmed these experiments, and 

 showed conclusively that, under favourable conditions, the juice acted 

 outside the body, and also that it haft a marked action in preventing 

 putrefaction. 



Between 1825 and 1833 Beaumont published his classical observa- 

 tions on Alexis St. Martin. In 1834, Eberle 2 discovered a method of 

 preparing an artificial gastric juice, which possessed all the digestive 

 properties of the normal secretion, by acting on the gastric mucous 

 membrane with dilute hydrochloric acid. Schwann 3 in 1836 gave the 

 name pepsin to the active principle to which he supposed the gastric 

 juice owed its activity. 



Products of peptic digestion. The first exact investigations into 

 the nature of the products of gastric digestion are those of Meissner 4 

 and his pupils. After digestion in acid solution and filtration, a pre- 

 cipitate was obtained on nearly neutralising, to which the name of 

 parapeptone was given. 



There is a considerable difference of opinion among various authors as to 

 what this parapeptone of Meissner is represented by in our more modern nomen- 

 clature. By some it is stated to have been syntonin. If Meissner had used a 

 strongly peptic digestive medium, filtered and neutralised, just after the bulk 

 of the proteid was dissolved, he would undoubtedly have obtained syntonin or 

 acid albumin ; but from his description it is evident that he was dealing 

 with a substance afterwards discovered by Kiihne, and renamed antialbumate. 

 This substance seems by its behaviour to be indeed a close ally of acid 

 albumin, and is obtained most readily by a more prolonged action of dilute 

 acids at 40 C. than is necessary to form acid albumin. It is also formed to 

 a small extent in a weak peptic digestive medium, probably from a similar 

 cause. Like acid (or alkali) albumin, it is insoluble in water, but easily 

 soluble in even very dilute acids or alkalies ; but it differs from acid albumin 

 in that when once formed it is not attacked by any pepsin in acid solution 

 by which acid albumin is actively peptonised. It is, however, convertible into 

 peptone (antipeptone) by the action of pancreatic juice, no leucine or tyrosine 

 being simultaneously formed. Meissner was undoubtedly using very weak 

 solutions of pepsin, and the action he obtained approximated to the prolonged 

 action of weak acids alone at 40 C. The action of the pepsin present was 

 too weak to catch, as it were, all the acid albumin on its way into antialbumate 

 and peptonise it ; and when once any antialbumate was formed, it could not then 

 be attacked and peptonised. Meissner's product was thus almost purely anti- 



" De alhnentornm concoctione," Edin., 1777. 



2 "Physiol. d. Verdauung nach Versuch.," AViirzburg, 1834. 



3 Arch.f. Anat., Physiol. u. wissensch. Med., 1836, S. 90. 



4 Ztschr. /. rat. Med., 1859-1862, Dritte Reihe, Bd. vii. S. 1 ; viii. S. 280 ; x. S. 1 ; 

 xii. S. 46 ; xiv. S. 303. Reviewed in Biol. CentralbL, Erlangen, 1884, Bd. iv. S. 

 407. 



