CHAP. XI. GENERAL SUMMARY. 2G9 



an alkali, which entirely arrested the process of diges- 

 tion, this immediately recommencing as soon as the 

 alkali was neutralised by a little weak hydrochloric 

 acid. From trials made with a large number of 

 substances, it was found that those which the secretion 

 of Drosera dissolves completely, or partially, or not 

 at all, are acted on in exactly the same manner by 

 gastric juice. We may, therefore, conclude that the 

 ferment of Drosera is closely analogous to, or identical 

 with, the pepsin of animals. 



The substances which are digested by Drosera act 

 on the leaves very differently. Some cause much 

 more energetic and rapid inflection of the tentacles, 

 and keep them inflected for a much longer time, than 

 do others. We are thus led to believe that the 

 former are more nutritious than the latter, as is 

 known to be the case with some of these same sub- 

 stances when given to animals ; for instance, meat in 

 comparison with gelatine. As cartilage is so tough a 

 substance and is so little acted on by water, its 

 prompt dissolution by the secretion of Drosera, and 

 subsequent absorption, is, perhaps, one of the most 

 striking cases. But it is not really more remarkable 

 than the digestion of meat, which is dissolved by this 

 secretion in the same manner and by the same stages 

 as by gastric juice. The secretion dissolves bone, and 

 even the enamel of teeth, but this is simply due to 

 the large quantity of acid secreted, owing, apparently, 

 to the desire of the plant for phosphorus. In the 

 case of bone, the ferment does not come into play 

 until all the phosphate of lime has been decomposed 

 and free acid is present, and then the fibrous basis is 

 quickly dissolved. Lastly, the secretion attacks and 

 dissolves matter out of living seeds, which it some- 

 times kills, or injures, as shown by the diseased state 



