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 had a marked action in preventing 
putrefaction. 
Between 1S25 and 1833 Beaumont published his classical observa- 
tions on Alexis St. Martin. In 1S34, 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 Kuhne, 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- 
1 " De aliinentonuu concoetione,"' Edin., 1777. 
2 "Physiol, d. Verdauung nach Versuch.," Wurzburg, 1834. 
3 Arch. f. Anat., Physiol, u. wissensch. Med., 1S36, S. 90. 
4 Ztschr. f. rat. Med., 1859-1862, Dritte Reilie, Bd. vii. S. 1 ; viii. S. 280 ; x. S. 1 ; 
xii. S. 46; xiv. S. 303. Reviewed in Biol. Centralbl.. Erlangen, 1SS4, Bd. iv. S. 
407. 
