DR DAVY'S OBSERVATIONS ON BLOOD AND MILK. 69 



Extending the analogy to vegetable substances, it seemed likely that all those 

 which contain albuminous matter, similar to casein, may be affected when boiled 

 with serum or white of egg, in the same manner as milk ; and the result of a 

 trial, with a mixture of serum and a strong emulsion of sweet almonds, has con- 

 firmed the inference. After boiling, the fluid expressed from the coagulima was 

 not precipitated by acetic acid. 



As the serum of the blood of even the same species of animal is liable to 

 slight variations, affecting the degree of temperature at which it coagulates, and, 

 as milk is subject to some variation, in regard to the same quality, as indicated 

 by the effect of rennet — a variation, perhaps, most of all depending on season of 

 the year, and the time that the milk has been exposed to the atmosphere — should 

 the experiments I have described be repeated, some little difference in the results 

 may perhaps be perceived, depending on the cu-cumstances just referred to. 



The action of one animal fluid on another, and those so similar as regards 

 their albuminous part, as milk and serum, offers curious matter for speculation, 

 and may be deserving of special attention, not only in relation to the culinary art, 

 and processes of manufacture in which vegetable juices are concerned, but also in 

 connexion with physiology. It may be found that the principle of rennet exists 

 in the blood, and that the analogous power of both, as regards the coagulation of 

 milk, depends on the same cause ; and, if so, then it may be farther deserving of 

 attention, in connexion with pathology and processes of morbid softening. 



The Oaks, Ambleside, 

 February 17. 1845. 



