80 DROSERA ROTUNDIFOLIA. CHAP. V 



on with other substances, and it was found to act most ener- 

 getically, but as no exact account of these trials was kept, they 

 are not here introduced. 



Mucus. Thick and thin mucus from the bronchial tubes, 

 placed on three leaves, caused inflection. A leaf with thin 

 mucus had its marginal tentacles and blade somewhat curved 

 inward in 5 hrs. 80 m., and greatly so in 20 hrs. The action of 

 this fluid no doubt is due either to the saliva or to some albu- 

 minous matter* mingled with it, and not, as we shall see in the 

 next chapter, to rnucin or the chemical principle of mucus. 



Saliva. Human saliva, when evaporated, yieldsf from 1'14 to 

 1'19 per cent, of residue ; and this yields 0'25 per cent, of ashes, 

 so that the proportion of nitrogenous matter which saliva con- 

 tains must be small. Nevertheless, drops placed on the discs of 

 eight leaves acted on them all. In one case all the exterior ten- 

 tacles, excepting nine, were inflected in 19 hrs. 30 m. ; in another 

 case a few became so in 2 hrs., and after 7 hrs. 30 m. all those 

 situated near where the drop lay, as well as the blade, were 

 acted on. Since making these trials, I have many scores of 

 times just touched glands with the handle of my scalpel wetted 

 with saliva, to ascertain whether a leaf was in an active condi- 

 tion ; for this was shown in the course of a few minutes by the 

 bending inwards of the tentacles. The edible nest of the Chinese 

 swallow is formed of matter secreted by the salivary glands ; two 

 grains were added to one ounce of distilled water (one part to 218), 

 which was boiled for several minutes, but did not dissolve the 

 whole. The usual-sized drops were placed on three leaves, and 

 these in 1 hr. 30 m. were well, and in 2 hrs. 15 m. closely, 

 inflected. 



Ixinylass. Drops of a solution about as thick as milk, and of 

 a still thicker solution, were placed on eight leaves, and the ten- 

 tacles of all became inflected. In one case the exterior tentacles 

 were well curved in after 6 hrs. 30 m., and the blade of the leaf 

 to a partial extent after 24 hrs. As saliva acted so efficiently, 

 and yet contains so small a proportion of nitrogenous matter, I 

 tried how small a quantity of isinglass would act. One part was 

 dissolved in 218 parts of distilled water, and drops were placed 

 on four leaves. After 5 hrs. two of these were considerably and 

 two moderately inflected ; after 22 hrs. the former were greatly 

 and the latter much more inflected. In the course of 48 hrs. 



* Mucus from the air-passages to contain some albumen, 

 is said in Marshall, 'Outlines of t M tiller's 'Elements of Physio 

 Physiology,' vol. ii. 1867, p. 3C4, logy,' Eng. Trans, vol. i. p. 5H. 



