PEPSIN. 49 



upon the only course which can lead to definite limits when he 

 precipitated the natural gastric juice with alcohol; unless too 

 much alcohol be added, the greater part of the peptones, and also 

 of the aqueous extractive matter of the saliva, remains in solution, 

 as indeed does a little pepsin. The precipitate dissolves pretty 

 freely in water, from which it is precipitated by corrosive subli- 

 mate,, protochloride of tin, basic acetate of lead, and tannic acid, 

 and in an imperfect manner by neutral acetate of lead ; it does not 

 become turbid on boiling, exhibits strong digestive properties when 

 treated with dilute hydrochloric or with lactic acid, but, like the 

 gastric juice, is deprived of them by boiling, by absolute alcohol, 

 and by neutralization with alkalies ; in an alkaline solution it very 

 soon becomes putrid, and in a neutral one it seems to give rise to 

 the formation of fungi ; but when rendered acid, it remains for a 

 very long time without suffering decomposition, exactly as natural 

 gastric juice. Frerichs has proved that the flocks precipitated by 

 alcohol contain sulphur and nitrogen. 



We shall discuss the true sources of the pepsin, the gastric 

 glands, and their contents, in the histologico-chemical part of this 

 work. 



C. Schmidt* has propounded a very interesting view regarding 

 the nature of the digestive principle ; he regards it as a conjugated 

 acid, whose negative constituent is hydrochloric acid, with Was- 

 mann's non-acid or coagulated pepsin as an adjunct, and assumes 

 that it possesses the property of entering into soluble combinations 

 with albumen, glutin, chondrin, &c.; according to him, it more 

 nearly resembles ligno-sulphuric acid than any other conjugated 

 acid, and as this becomes disintegrated into dextrin and sulphuric 

 acid, so the pepsin-hydrochloric acid becomes separated at 100 

 into Wasmann's coagulated pepsin arid hydrochloric acid, and in 

 either case it is equally impossible to reproduce the conjugated 

 acid from its proximate elements after their separation. On 

 bringing the complex acid in contact with an alkali, the adjunct 

 the substance which has been in combination with the hydro- 

 chloric acid is precipitated. Schmidt believes that he has ascer- 

 tained that an artificial digestive mixture which has expended its 

 solvent and digestive powers, regains them on the addition of free 

 acid; and that when hydrochloric acid is added, the pepsin- 

 hydrochloric acid is expelled from its combination with albumen, 

 &c., and thus regains its former properties, while the newly added 



* De digestionis natura etc. Diss. inaug. Dorp. Liv. 1846 ; and Ann. d 

 Ch. u. Pharm. Bd. 61, S. 22-24. 



VOL. u. E 



