Cuar. VI.J DIGESTION. 109 
which has been kept for some time, and gluten which has 
heen subjected to weak hydrochloric acid, act more quickly 
than these substances in their fresh state. 
The length of time during which the tentacles remain 
inflected largely depends on the quantity of the substance 
given, partly on the facility with which it is penetrated or 
acted on by the secretion, and partly on its essential nature. 
The tentacles always remain inflected much longer over 
large bits or large drops than over small bits or drops. 
Texture probably plays a part in determining the extra- 
ordinary length of time during which the tentacles remain 
inflected 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; phos- 
phorus 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 integu- 
ments; for animal matter is soon extracted from insects 
(probably by exosmose from their bodies into the dense sur- 
rounding 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 flesh 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, justi- 
fied 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 
interesting 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 inflected for a 
longer time, than does gelatine, or areolar tissue, or the 
fibrous basis of bone. It is not known how long an animal 
* See the classification adopted by Dr. Michael Foster in Watts’ ‘Dict. of 
Chemistry,’ Supplement 1872, p. 969. 
