172 Butter Churning. [Sept., 



like the substance of the nerves and brain, because the influence 

 of life is no longer exerciseil upon it? 



Of the preparation of rennet, and the use of the curd in the cafs 

 stomach. 



Curious (liflTerences in opinion and practice prevail in diary 

 districts, in regard to the preparation of rennet. These differences 

 are all interesting, because they are almost in every case connect- 

 ed with minute chemical operations, and because a critical exam- 

 ination of them gives rise to theoretical suggestions, which may 

 lead to improvements in practice. 



Of this kind is the diiference which prevails as to the use or 

 usefulness of the curd in the stomach of the calf, when employed 

 for the preparation of rennet. 



Three different practices are followed in different districts in 

 preparing the stomach of the suckling or milk-fed calf for salting. 

 Some carefully wash ever-y thing out of the stomach, some salt 

 the stomach and its iirilky contents together, or take out the cui'd 

 and salt it separately; and some give the calf before it is killed a 

 large draught of milk, that the quantity of curd in the stomach 

 may be greater at ihe time when it is taken from the animal, and 

 put into the salting-tub.* 



Which of these three practices is the best? Is the cui'd of any 

 use at all in the preparation of rennet? 



An answer to these questions is supplied by a knowledge of the 

 way in which rennet acts in curdling irrilk, and of the nature of 

 the substances which, like rennet, possess this remarkable proper- 



In my published Lectures on Agricultural Chemisty and Geolo- 

 gy, second edition, p. 985, I have endeavored to show, that the 

 action of rennet consists simply iir the rapid conversion of a por-- 

 tion of the milk sugar into lactic acid, which acid has, like vine- 

 gar, the property of curdling milk. I have stated also that a 

 similar property is possessed by animal membranes of various 

 kinds, after they have been for some time exposed to the air, and 

 even by the curd of milk itself. 



From these facts, it appear's that the curd in the calf's stomach 

 naturally posseses the same power of curdling milk which the 

 membrane of the stomach itself is valued for, and therefore ought 

 not to be rejected. 



And yet the discoi-dant practices to which I have alluded are 

 all justifiable and perfectly concordant. 



In Gloucester and Cheshire, the curd and slimy matters are usu- 



• See my Lectures on Agricultural Chemistry and Geology, 2J ed., p. 980. 



