108 DROSERA ROTUNDIFOLIA. (Cuar. VI. 
acted on in the same manner, both by the secretion of Drosera 
and gastric juice. But this substance, as well as the so- 
called hematin used by me, ought perhaps to have been 
classed with indigestible substances. 
That gastric juice acts by means of its ferment, pepsin, 
solely in the presence of an acid, is well established; and 
we have excellent evidence that a ferment is present in the 
secretion of Drosera, which likewise acts only in the presence 
of an acid; for we have seen that when the secretion is 
neutralised by minute drops of the solution of an alkali, the 
digestion of albumen is completely stopped, and that on 
the addition of a minute dose of hydrochloric acid it imme- 
diately recommences. 
The nine following substances, or classes of substances, 
namely epidermic productions, fibro-elastic tissue, mucin, 
pepsin, urea, chitine, cellulose, gun-cotton, chlorophyll, starch, 
tat and oil, are not acted on by the secretion of Drosera ; 
nor are they, as far as is known, by the gastric juice of 
animals. Some soluble matter, however, was extracted from 
the mucin, pepsin, and chlorophyll, used by me, both by the 
secretion and by artificial gastric juice. 
The several substances, which are completely dissolved by 
the secretion, and which are afterwards absorbed by the 
glands, affect the leaves rather differently. ‘They induce 
inflection at very different rates, and in very different 
degrees ; and the tentacles remain inflected for very different 
periods of time. Quick inflection depends partly on the 
quantity of the substance given, so that many glands are 
simultaneously affected, partly on the facility with which it 
is penetrated, and liquefied by the secretion, and partly on 
its nature, but chiefly on the presence of exciting matter 
already in solution. ‘hus saliva, or a weak solution of raw 
meat, acts much more quickly than even a strong solution of 
gelatine. So again leaves which have re-expanded, after 
absorbing drops of a solution of pure gelatine or isinglass 
(the latter being the more powerful of the two), if given bits 
of meat, are inflected much more energetically and quickly 
than they were before, notwithstanding that some rest is gener- 
ally requisite between two acts of inflection. We probably 
see the influence of texture in gelatine and globulin when 
softened by having been soaked in water acting more quickly 
than when merely wetted. It may be partly due to changed 
texture, and partly tochanged chemical nature, that albumen, 
