140 MILK . [vin 



only effect a certain amount of fermentative work, 

 which can be definitely measured, there is no limit 

 to the amount of work the organised ferment may 

 effect. As already pointed out, a most important 

 relationship exists between these two ferments ; for 

 most true ferments give rise to a chemical ferment, 

 which is one of the products of their action. It is 

 on this account often very difficult to know whether 

 certain fermentative changes are caused by the true 

 or the chemical ferment. 



Coagulating Power of Rennet. As has been 

 pointed out, the amount of work which unorganised 

 ferments can effect is capable of being definitely meas- 

 ured. Now some conception of the coagulating power 

 of rennet is afforded by the following short description 

 of an experiment carried out by Soldner, a German 

 investigator. He prepared an extract of rennet by 

 treating the dry stomach of a calf with a 5 per cent 

 solution of salt. The rennet was then precipitated, 

 in the form of a grayish-brown powder, by adding 

 more salt. He found that one part of this powder in 

 the dry state was able to coagulate, in forty minutes, 

 at a temperature of 35 C. (95 Fahr.), one million 

 parts of milk. On analysis, he found that this 

 brown powder only contained 36 per cent of organic 

 matter ; and as this 36 per cent was probably not 

 the pure rennet, the inference is that one part of 

 pure rennet can coagulate, at the above temperature 



