STOMACH AND INTESTINE. 



333 



differs chiefly in containing about 2 per cent, 

 more nitrogen. 



The addition of a few drops of dilute 

 muriatic acid to a solution of this precipitate 

 in cold water, constitutes a liquid which 

 possesses energetic solvent powers over ordi- 

 nary animal food. Hence the organic sub- 

 stance itself has been termed pepsine (Wtfr<n?, 

 concoctio) : a name to which there can be no 

 objection, so long as its meaning is confined 

 within proper limits ; and is not extended 

 to imply a single and definite organic com- 

 pound, capable of digesting all the aliment- 

 ary principles.* 



The chemical properties of pepsine offer a 

 striking resemblance to those of many albu- 

 minous compounds. Its chief differences from 

 these substances seem to consist in the fact, 

 that it is little or not at all precipitated from 

 its watery solution, by some of the salts which 

 would throw down dissolved albumen. But 

 the precise degree of this resemblance has 

 been found to vary greatly in different obser- 

 vations. Nor is this want of uniformity sur- 

 pizing. For, as Frerichs has pointed outf, 

 the various watery extracts of stomach made 



* Here, again, the author thinks it better to sub- 

 join in a foot-note the successive additions to our 

 knowledge that have gradually built up the brief 

 statement of the text, to which many readers will 

 probably prefer limiting their attention. 



As before mentioned, Reaumur, Spallanzani, and 

 Carminati, may be regarded as having collectively 

 determined that the gastric juice is an acid, anti- 

 septic liquid, secreted on the introduction of food, 

 and capable of dissolving certain alimentary sub- 

 stances, even when removed from the body. 



The first attempt to analyze the organic matters 

 of the gastric juice was made by Tiedemann and 

 Gmelin (Loc. cit.). They announced the presence 

 of mucus ; an alcoholic extract or osmazome ; and 

 a substance, soluble in water and precipitated by 

 various metallic salts, which they stated to be Ptya- 

 line. 



Eberle (Physiologic der Yerdauung, Wuerzburg, 

 1834) adopted a more synthetical method of inquiry. 

 He found that the addition of dilute acids to an in- 

 fusion of the gastric mucous membrane formed an ar- 

 tificial digestive fluid. Schwann (Mueller's Archiv. 

 1836. pp. 70. et seq., 90. et seq. : and PoggendorfPs 

 Annalen, Bd. xxxviii. p. 358.) went still further. 

 He found that it was only the glandular part of the 

 stomach which possessed this power. And by pre- 

 viously removing the albumen of a gastric infusion, 

 and neutralizing its acid, he was enabled to preci- 

 pitate with bichloride of mercury a substance, 

 which, when mixed with very dilute hydrochloric 

 acid, and freed from this metal, formed a powerful 

 digestive agent. He therefore named it Pepsine. 

 Wasmann (Loc. cit.) adopted a different method. 

 He precipitated a very carefully prepared watery 

 extract of stomach with acetate of lead or bichloride 

 of mercury. After removing the metal and acid, he 

 threw down the pepsine by alcohol, and thus puri- 

 fied it from osmazome, which is soluble in this liquid. 



The various observers who have since corrobo- 

 rated Wasmann's statements do not seem to have ef- 

 fected any important improvement in this process. 

 Amongst these we may enumerate Pappenheim (Zur 

 Kenntniss der Verdauung, Breslau, 1839), Valentin 

 (Kepertorium, B. i., s. 64.), Elsaesser (Magenerwei- 

 chung der Saueglinge, Stuttgart, 1846), Buchheim 

 (De Albumine, Pepsino, et Muco. Lipsiae. 1845), 

 Vogel (Op. cit.), Lehmann (Loc. cit.), Scherer, 

 Stannius, and many others. 



t Op. cit. p. 785" 



use of in such experiments have all been mix- 

 tures of gastric juice with a variable quantity 

 of albuminous matters, from which substances 

 the pepsine is but partially set free by the sub- 

 sequent process of purification. To this fact 

 we may add, that it is not impossible the 

 quantity and quality of the mineral constitu- 

 ents contained in these impurities have also 

 affected the results. Frerichs therefore exa- 

 mined a quantity of the gastric secretion, 

 which had been obtained from fistulae ; and 

 from dogs who had been made to swallow in- 

 digestible substances, such as pebbles and 

 peppercorns. In such cases saliva would pro- 

 bably form the only impurity. 



The reactions of gastric juice, and probably 

 of pure pepsine, are as follows : it is not preci- 

 pitated by boiling, by ferro-cyanide of potas- 

 sium, sulphate of copper, alum, chloride of iron, 

 or mineral acids. It is precipitated, though not 

 completely, by bi-chloride of mercury. Car- 

 bonates of the alkalies give a precipitate of its 

 lime salts. And the soluble salts of silver and 

 lead throw down the chlorides of these metals. 

 In all of these instances a portion of the pep- 

 sine is carried down with the precipitate. In 

 the case of the lead, the greater part of the 

 pepsine is thus deposited ; but almost all of 

 it may be recovered by washing. 



Action of the gastric juice. It is to the 

 repeated and careful experiments on artificial 

 digestion, which were begun by Eberle, and 

 continued by the various observers before 

 alluded to*, that our knowledge of the details 

 of stomach-digestion is chiefly due. This 

 method of inquiry has not only allowed a 

 continuous and close inspection of changes 

 which must have escaped observation in the 

 living body, but has so varied the several 

 conditions of the solvent process, as almost 

 to acquaint us with the share which each 

 takes in the final and united result. In short, 

 these "questionings of nature" have so far 

 been answered, that we may be said to know, 

 not only what substances the stomach digests, 

 but by what means it digests them. Of the 

 nature of this process, however, we are still 

 ignorant ; or at most, can only find in its cir- 

 cumstances some analogies, such as may 

 justify and support a few vague conjectures 

 respecting it. 



Temperature exercises an important in- 

 fluence on the gastric solvent. At the or- 

 dinary temperature of the atmosphere, the 

 action of the gastric juice is scarcely percep- 

 tible, even when continued during many 

 hours.y Lower degrees of cold suspend its 

 action still more completely. Heated to the 

 temperature of the body namely, to about 

 100 Fahrenheit it acts very energetically. 

 A further accession of temperature at first 

 increases, but soon injures, and finally for ever 

 destroys, all its digestive powers. The precise 

 point at which this change of effect occurs is 

 not clearly known; but it is probably at or near 

 120. The dried pepsine of the artificial digest- 



* In the foot-note to this page, 

 f Beaumont, Op. cit. p. 146. 



