114 DROSERA ROTUNDIFOLIA. Chap. VI. 



from the leaves, and this is likewise characteristic of 

 chemically prepared casein. Minute drops of milk, 

 placed on leaves, were coagulated in about ten 

 minutes. Schiff denies* that the coagulation of milk 

 by gastric juice is exclusively due to the acid w^hich 

 is present, but attributes it in part to the pepsin; 

 and it seems doubtful whether with Drosera the 

 coagulation can be wholly due to the acid, as the 

 secretioii does not commonly colour litmus paper 

 until the tentacles have become well inflected ; 

 whereas the coagulation commences, as we have seen, 

 in about ten minutes. Minute drops of skimmed 

 milk were placed on the discs of five leaves ; and a 

 large proportion of the coagulated matter or curd 

 was dissolved in 6 hrs. and still more completely 

 in 8 hrs. These leaves re-expanded after two days, 

 and the viscid fluid left on their discs was then care- 

 fully scraped off and examined. It seemed at first 

 sight as if all the casein had not been dissolved, for 

 a little matter was left which appeared of a whitish 

 colour by reflected light. But this matter, when 

 examined under a high power, and when compared 

 with a minute drop of skimmed milk coagulated by 

 acetic acid, was seen to consist exclusively of oil- 

 globules, more or less aggregated together, with no 

 trace of casein. As I was not familiar with the 

 microscopical appearance of milk, I asked Dr. Lauder 

 Brunton to examine the slides, and he tested the 

 globules with ether, and found that they were dis- 

 solved. We may, therefore, conclude that the secretion 

 quickly dissolves casein, in the state in which it exists 

 in milk. 



Chemically Prepared Casein.--T\i\^ substance, which 



♦ 'Le9ons,' &c. torn. ii. p. 151. 



