Cuar, VI. DIGESTION. 125 
were placed on some leaves, and after these had re-expanded, 
the pieces were carefully examined. Their angles were as 
sharp as ever, and they did not differ in appearance from the 
other wing and elytron of the same insect which had been left 
in water. The elytron, however, had evidently yielded some 
nutritious matter, for the leaf remained clasped over it for four 
days; whereas the leaves with bits of the true wing re-expanded 
on the second day. Any one who will examine the excrement 
of insect-eating animals will see how powerless their gastric 
juice is on chitine. 
Cellulose—I did not obtain this substance in a separate state, 
. but tried angular bits of dry wood, cork, sphagnum moss, linen, 
and cotton thread. None of these bodies were in the least 
attacked by the secretion, and they caused only that moderate 
amount of inflection which is common to all inorganic objects. 
Gun-cotton, which consists of cellulose, with the hydrogen 
replaced by nitrogen, was tried with the same result. We have 
seen that a decoction of cabbage-leaves excites the most power- 
ful inflection. I therefore placed two little square bits of the 
blade of a cabbage-leaf, and four little cubes cut from the 
midrib, on six leaves of Drosera. These became well inflected 
in 12 hrs., and remained so for between two and four days; 
the bits of cabbage being bathed all the time by acid secre- 
tion. This shows that some exciting matter, to which I shall 
presently refer, had been absorbed; but the angles of the 
squares and cubes remained as sharp as ever, proving that the 
framework of cellulose had not been attacked. Small square 
bits of spinach-leaves were tried with the same result; the 
glands pouring forth a moderate supply of acid secretion, 
and the tentacles remaining inflected for three days. We have 
also seen that the delicate coats of pollen grains are not dissolved 
by the secretion. It is well known that the gastric juice of 
animals does not attack cellulose. 
Chlorophyll.—This substance was tried, as it contains nitrogen. 
Dr. Moore sent me some preserved in alcohol; it was dried, but 
soon deliquesced. Particles were placed on four leaves; after 
38 hrs. the secretion was acid; after 8 hrs. there was a good deal 
of inflection, which in 24 hrs. became fairly well marked. After 
four days two of the leaves began tu open, and the other two 
were then almost fully re-expanded. It is therefore clear that 
this chlorophyll contained matter which excited the leaves to a 
moderate degree; but judging by the eye, little or none was dis- 
solved ; so that in a pure state it would not probably have been 
attacked by the secretion. Dr. Sanderson tried that which I 
