Chap. V.] EFFECTS OF ORGANIC FLUID. 67 



the tentacles of six of them to be well inflected. In one case the edge 

 of the leaf itself became much curled in after 20 hrs. The one leaf 

 which was unaffected remained so for 26 hrs., and was then treated 

 with a drop of milk, and this caused the tentacles to bend inwards 

 in 12 hrs. 



Cold Filtered Infusion of Raw Meat. This was tried only on a 

 single leaf, which had most of its outer tentacles and the blade in- 

 flected in 19 hrs. During subsequent years I repeatedly used this 

 infusion to test leaves which had been experimented on with other 

 substances, and it was found to act most energetically, 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 inwards in 5 hrs. 

 30 m. and greatly so in 20 hrs. The action of this fluid no doubt is 

 due either to the saliva or to some albuminous matter ^ mingled with 

 it, and not, as we shall see in the next chapter, to mucin or the 

 chemical principle of mucus. 



Saliva. Human saliva, when evaporated, yields* 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 contains 

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

 leaves acted on them all. In one ease all the exterior tentacles, ex- 

 cepting 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 mak- 

 ing these trials, I have many scores of times just touched the glands 

 with the handle of my scalpel wetted with saliva, to ascertain 

 whether a leaf was in an active condition ; for this was shown in the 

 course of a few minutes by the bending inwa^ls 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 dis- 

 tilled 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. 



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

 still thicker solution, were placed on eight leaves, and the tentacles 

 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 ex- 

 tent after 24 hrs. As saliva acted so eflTiciently, and yet contains so 

 small a proportion of nitrogenous matter, I tried how small a quan- 

 tity 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. from the time when the drops were placed 



' Mucus from the air-passages * MUIIer's * Elements of Physl- 



is snld in MarHhall, * Outlines of olofry,' Eng. translatioD, vol. I. 

 I'hysloloBV.' vol. il. 1867, p. 304, p. 514. 

 to coutaiu some albumen. 

 6 



