94 DROSERA ROTUNDIFOLIA. [Chap. VI. 



This acted most powerfully, for after only 3 hrs. 30 m. all 

 four leaves were strongly inflected. Three of them began to 

 re-expand after 24 hrs., and in 48 hrs. were completely open; 

 but the fourth had only partially re-expanded. All the lique- 

 fied chondrin was by this time absorbed. Hence a solution 

 of chondrin seems to act far more quickly and energetically 

 than pure gelatine or isinglass; but I am assured by good 

 authorities that it is most difficult, or impossible, to know 

 whether chondrin is pure, and if it contained any albuminous 

 compound, this would have produced the above effects. 

 Nevertheless, I have thought these facts worth giving, as 

 there is so much doubt on the nutritious value of gelatine; 

 and Dr. Lauder Brunton does not know of any experiments 

 with respect to animals on the relative value of gelatine and 

 chondrin. 



Milk. We have seen in the last chapter that milk acts 

 most powerfully on the leaves; but whether this is due to 

 the contained casein or albumen, I know not, liather large 

 drops of milk excite so much secretion (which is very acid) 

 that it sometimes trickles down from the leaves, and this is 

 likewise characteristic of chemically prepared casein. Min- 

 ute drops of milk, placed on leaves, were coagulated in about 

 ten minutes. SchiF 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; where- 

 as 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 com- 

 pletely 1'. 8 hrs. Those leaves re-expanded after two days, 

 and thJ viscid fluid left on their discs was then carefully 

 scrap. 4 off and examined. It seemed at first sight as if all 

 the C4^ein had not been dissolved, for a little matter was 

 left vifcich 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 coagru- 

 latcd i>y acetic acid, was seen to consist exclusively of oil- 

 ** ' Lecons,' &c. torn. li. p. 15L 



