Oxap, VI. DIGESTION. ST 
these fourteen leaves had become more or less in- 
flected, I again tested the secretion, selecting glands 
which had not as yet reached the centre or touched 
any object, and it was now plainly acid. The degree 
of acidity of the secretion varied somewhat on the 
glands of the same leaf. On some leaves, a few ten- 
tacles did not, from some unknown cause, become in- 
flected, as often happens; and in five instances their 
secretion was found not to be in the least acid; 
whilst the secretion of the adjoining and inflected 
tentacles on the same leaf was decidedly acid. With 
leaves excited by particles of glass placed on the 
central glands, the secretion which collects on the 
disc beneath them was much more strongly acid 
than that poured forth from the exterior tentacles, 
which were as yet only moderately inflected. When 
bits of albumen (and this is naturally alkaline), or 
bits of meat were placed on the disc, the secretion 
collected beneath them was likewise strongly acid. 
As raw meat moistened with water is slightly acid, I 
compared its action on litmus paper before it was 
placed on the leaves, and afterwards when bathed in 
the secretion ; and there could not be the least doubt 
that the latter was very much more acid. I have 
indeed tried hundreds of times the state of the secre- 
tion on the discs of leaves which were inflected over 
various objects, and never failed to find it acid. We 
may, therefore, conclude that the secretion from un- 
excited leaves, though extremely viscid, is not acid or 
only slightly so, but that it becomes acid, or much 
more strongly so, after the tentacles have begun to 
bend over any inorganic or organic object; and still 
more strongly acid after the tentacles have remained 
for some time closely clasped over any object. 
I may here remind the reader that the secretion 
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