Chap. XVI]. SECRETION, ABSORPTION, DIGESTION. 315 



obser\-ed the above six small particles during several days, but 

 they did not seem in the least reduced in bulk. A particle was 

 also left for two days in a little pool of secretion, which had run 

 down from a piece of spinach leaf; but although the particle was 

 so minute no diminution was perceptible. We may therefore con- 

 clude that the secretion cannot dissolve starch. The increase 

 caused by this substance may, I presume, be attributed to exos- 

 mose. But I am surprised that starch acted so quickly and power- 

 fully as it did, though in a less degree than sugar. Colloids are 

 known to possess some slight power of dialysis; and on placing 

 the leaves of a Primula in water, and others in syrup and dif- 

 fused starch, those in the starch became flaccid, but to a less de- 

 gree and at a much slower rate than the leaves in the syrup; 

 those in water remaining all the time crisp. 



From the foregoing experiments and observations we see 

 that objects not containing soluble matter have little or no 

 power of exciting the glands to secrete. Non-nitrogenous 

 fluids, if dense, cause the glands to pour forth a large supply 

 of viscid fluid, but this is not in the least acid. On the 

 other hand, the secretion from glands excited by contact 

 with nitrogenous solids or liquids is invariably acid, and is 

 80 copious that it often runs down the leaves and collects 

 within the naturally incurved margins. The secretion in 

 this state has the power of quickly dissolving, that is of 

 digesting, the muscles of insects, meat, cartilage, albumen, 

 fibrin, gelatine, and casein as it exists in the curds of milk.* 

 The glands are strongly excited by chemically prepared 

 casein and gluten; but these substances (the latter- not 

 having been soaked in weak hydrochloric acid) are only 

 partially dissolved, as was likewise the case with Drosera. 

 The secretion, when containing animal matter in solution, 

 whether derived from solids or from liquids, such as an 

 infusion of raw meat, milk, or a weak solution of carbonate 

 of ammonia, is .quickly absorbed; and the glands, which 

 were before limpid and of a greenish colour, become brownish 

 and contain masses of aggregated granular matter. This 

 matter, from its spontaneous movements, no doubt consists 



[Pfeffer (' Ueber flelschfes- to the nm use In the Italian 



sende PflnnBen,' In the ' Land- Alps. The property of the plant 



wIrthBchaft. Jahrbficher.' 1877) seems to be widely known amon;; 



quotes Linnaeus (' Flora Lappon- primitive people, for. within the 



lea,' 1737, p. 10 to the effect last 30 years. It wan used as ren- 



that certain Lapland tribes use net by mountain farmers In Nor'h 



the leaves- of rinnnlcnla to coajf- Wales. I have myself succejnleU 



ulate milk. I'ft'fTer learnt from In cunllInK milk with this vegf- 



an old shepherd that they are put table rennet. F. D.] 



