CHEMICAL BASIS OF THE ANIMAL I'.oDV. r,i 



< -a!, him phosphate is then tillered off, washed, and di .d\ed in 

 dilute hydrochloric acid, and this solution is then dialysed until 

 it is five from chlorine and phosphate-, and >n acidulating with 

 hydrochloric acid is ready fur use. 



< hvinu' to tin- relatively slow diffiisil.ility of allmmn.se.s and peptoii.^. 

 men- dialysis "1 a solution of pepsin in which these suhstanc. 



:t does not. within any reasonalde time, siitlice to yield an e\eii 

 Comparatively pure solution of tin- en/yme. 



Many form- of commercially prepared pepsin arc ohtained l>y d. 

 iiii,' tin- irastric mucous nifinlirain- \\ith dilute hydrochloric acid; tin- 

 BOltttioD thus ohtaiiifd is thru >at uratt-d with soinc >alt siicli as Na<'l. 



, or CaCl... wlu-n-ujMin a .-cum rises to the surface, consisting 

 chiftly of j.rotcid niattt-i- to which the pepsin is adherent. This scum 

 is then removed, frequently mixed witli milk-sugar and dried at a low 

 temperature. 1 



IVpsin does not exist preformed in the cells <f tin- gastric 

 t^litijd s , hut as a /yinogen to which tin- name of iH.'j)sino^en i s 

 jivMi ; this is ivadily cunvciifd into pepsin by tin- action <f 

 hydrochloric acid. 2 



I'nlikc ptyalin the hydrolytic activity of pepsin igjmanifggted 

 ojily '" presence of an acii,l. The most ctlicu-nt acid in this 

 i for artificial digestions is hydrochloric of a strength of 

 '2 p. c. :j The average percentage of this acid may be statt-d a^ 

 '2 p. c. in normal gastric juice, but it varies slightly in the case 

 of different animals. 1 Other acids may lie substituted for tin- 

 hydrochloric, the optimal percentage varying for the se 

 acid 



A remarkalde peptonisin^ en/yme (papain). exits in tin- milky juice 

 of an Ma>t and \\'e>t Indian plant, Carica 1'apaya. Any di-criptimi 

 of thi> en/yme and its properties lies outside the scope ' this \\ork: 

 all necessary information may lie uhtaim-d 1-y referring to the pap.-i- 



(ploteil !ielo\\/' 



of jiejisin and other en/\ |iiently found in 



urine ; the literature of the subject up to the present date is fully 

 Diluted iii the papers to which a n-feiem is hnv " 



:, Mah >./ '. H'l. ill. (187.-H - 



-h), lt.nl. H 



KlM.-in iind Crut/.iM-r, I'Hu-.T 1 - Arr.h. 1M. \in. (IS74). S. \~>2 



\ , in. (1881), |. -\ an. I K.lkin.v /'/ Vl. vil. (\M), p. :I7I. 



.. 1'tlu^.TH .\,.l,. IM. \\\1 



KVII i I-- 



Bidder and s. -imii.it. I>" \'.,.i.i I amimUm 



I'tlntr.T's .\ ,<!,. IM. \i\ (1879), v 



, i.Uon iind Iii.-t.Tirl,. .!..,/,. f. .\,,,,i. . /'/,./>-./. Jali r. 1860, S. 6M. I 

 in Mah's Btrlckt. Mil. \. I 



Wnrte et Boachnt, r,,,,,,^ /,../. T. i\\\.\ \Vurt/. / 

 KO.B 1879; I KOI ! 787 I'"l;ik (l)ntdi). 8e Abt. in Mmly'f Jahntbtr. 



. M.,r-':../ //'/,./.<.../. V.,1. v 1 1-- M p. 336. 



..l.-lm:um. , 15. 1 IXli 



lIu-MMii) A!.-i in \: : I maim. l'Hui:'r'- 



I'.'l. M.I. (1887), S. 14!j. llclwea, Ibid. BI xi.m 



