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. — Tliick 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. 30 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 mucin 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 eon- 

 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. 



Isinglass. — 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 coEsiderably and 

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

 q,nd 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 f Miiller's 'Elements of Phy sio- 



Phy Biology,' vol. ii. 18G7, p. 364, logy,' Eng. Trans, vol. i. p. 514. 



