CHAP. VI, 



DIGESTION. 133 



over the hard grains of chemically prepared casein. 

 But the tentacles remain inflected for an equally long 

 time over finely powdered, precipitated phosphate of 

 lime ; phosphorus in this latter case evidently being 

 the attraction, and animal matter in the case of casein. 

 The leaves remain long inflected over insects, but it is 

 doubtful how far this is due to the protection afforded 

 by their chitinous integuments; for animal matter is 

 soon extracted from insects (probably by exosmose from 

 their bodies into the dense surrounding secretion), 

 as shown by the prompt inflection of the leaves. We 

 see the influence of the nature of different substances 

 in bits of meat, albumen, and fresh gluten acting very 

 differently from equal-sized bits of gelatine, areolar 

 tissue, and the fibrous basis of bone. The former 

 cause not only far more prompt and energetic, but 

 more prolonged, inflection than do the latter. Hence 

 we are, I think, justified in believing that gelatine, 

 areolar tissue, and the fibrous basis of bone, would be 

 far less nutritious to Drosera than such substances 

 as insects, meat, albumen, &c. This is an interest- 

 ing conclusion, as it is known that gelatine affords 

 but little nutriment to animals ; and so, probably, 

 would areolar tissue and the fibrous basis of bone. 

 The chondrin which I used acted more powerfully 

 than gelatine, but then I do not know that it was 

 pure. It is a more remarkable fact that fibrin, which 

 belongs to the great class of Proteids,* including 

 albumen in one of its sub-groups, does not excite 

 the tentacles in a greater degree, or keep them in- 

 flected for a longer time, than does gelatine, or 



* Pee the classification adopted by Dr. Miciiael Foster in \Vattcf 

 Diet, of Chemistry,' Supplement 1872, p. 969. 



