150 THE MILK-CURDLING ENZYME. [BOOK II. 



dilute sodium carbonate may be used as in the case of pepsinogen 

 and pepsin to distinguish zymogen from ferment 1 . 



4. High temperatures diminish, and ultimately destroy, the 

 activity of solutions of the curdling ferment, the result being remark- 

 ably influenced, however, by the reaction of the liquid. A liquid 

 which is very rich in ferment can be momentarily heated to 70 C. 

 without losing all its activity, whilst if the same liquid be acidulated 

 with 0*3 per cent, of HC1, momentary heating to 63 C. or digestion 

 at 37 40 C. for 40 hours, suffice completely to annul its milk- 

 curdling power. As pepsin is not destroyed by long digestion in acid 

 solutions, whilst the milk-curdling ferment is so destroyed, we can free 

 acid pepsin solutions from the curdling ferment by merely keeping 

 them for a sufficient time at 40 C. 



racteristic pro- The one g rea t characteristic of the rennet ferment 



perty of the is the power which it possesses of clotting solutions 



ferment is to of casein, providing these contain a sufficient quantity 



coagulate ca- o f lime salts, 

 sein. 



Without anticipating the complete treatment of this subject in 

 another volume of this work, it is necessary in this place to state that 

 comparatively recent researches of Hammarsten have established 

 that casein, as it exists in milk, is a body which can be precipi- 

 tated unaltered, by means of various agents, such as common salt, 

 magnesium sulphate and very weak acids. Under the influence of 

 rennet, however, casein probably undergoes a decomposition which 

 appears to resemble that of fibrinogen, as we conceive it to occur when 

 under the influence of the fibrin-ferment, it splits up with the sepa- 

 ration of fibrin. Casein under the influence of the ferment would 

 appear to split up into a proteid, which if lime salts be present, 

 assumes a clotted form, and into one which remains in solution. 



Paracasein To the solid product formed during the clotting of 



and -whey-ai- nrilk or of a solution of casein by milk, we may with 

 aumm g^ hey ~ propriety apply the name Paracasein, especially as this 

 appropriate term is the suggestion of Hammarsten, to 

 whose researches we are indebted for our present knowledge of the 

 clotting of casein. The soluble product of the decomposition is a 

 proteid, resembling the albumoses in its reactions, to which Ham- 

 marsten gives the name of Molkeneiweiss, or whey-albumin (why not 

 Molken-albumose or whey-albumose ?). 



The milk-curdling ferment does not convert milk-sugar into lactic 

 acid. 



Activity of Hammarsten precipitated a glycerin-extract of calf's 



the milk-curd- st omach with alcohol, and dissolved the precipitate in 



water. The amount of dissolved matter was then deter- 



1 Langley, Journal of Physiology, Vol. m. (1882), p. 287. 



