114 DROSERA ROTUNDIFOLIA. Cuap. VIL 
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 which 
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 
secretion 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.—This substance, which 
* ‘Lecons,’ &c. tom. ii. p. 151. 
