ORGANS OP DIGESTION. 87 



proportion of water, for drink : that is, as a solvent to 

 the more solid matters. Plants again, strictly speak- 

 ing, subsist on drink alone, being indeed incapable of 

 taking up any solid matter, at least till it be previously 

 dissolved or diffused in water. 



There is an obvious and well-known proof, that 

 plants live on water chiefly, if not altogether, derived 

 from hyacinths and other bulbs placed in glasses, and 

 supplied with water, in which they blow as well as in 

 a garden. It is found, however, that they do not 

 thrive unless the water is regularly changed, indi- 

 cating that it is not the water alone, but something in 

 the water, which becomes exhausted and deteriorated 

 by the feculent slime discharged by the plant. It has 

 also been found by experiment, that distilled water 

 will not support a healthy growth in plants, and most, 

 if not all species, when planted in pure calcined sand, 

 and watered with distilled water, quickly die, as they 

 do when quite deprived of water. 



From chemical analysis and experiment, it appears 

 that the chief matters taken up byjplants, besides water, 

 consist of carbonic acid gas and azote, or nitrogen, 

 chiefly in form of humic acid, together with a few 

 salts, such as potass, and out of these and the hydrogen 

 and oxygen of the water, all vegetable products seem 

 to be wholly or chiefly elaborated. 



M. Lassaigne proved that these all pass into the plant 

 from without, by the ingenious experiment of analysing 

 the chemical constituents of seeds before and after ger- 

 minating. 



When by chemical experiment substances are found 



