PROXIMATE ELEMENTS. 161 



Chemical composition of the Sap. 



The sap is a transparent, colourless fluid, imbibed by the 

 vegetable from the earth and air ; or more properly, from the 

 water existing in them, which holds in solution oxygen, hydro- 

 gen, carbon, nitrogen, earths, mineral-salts, and animal and 

 vegetable matter. We might suppose, that being derived from 

 the same source, the sap in all vegetables would be alike, but 

 it is never obtained pure ; it is mingled with the proximate 

 principles, or proper juices, and thus differs in different species 

 of vegetables ; water, however, constitutes the principal part 

 in all. 



The following result of the analysis of the sap of some 

 vegetables has been offered by a French chemist.* 



Sap of the. elm, (ULMUS campcstris,) water, volatile matter, 

 acetate of potash, carbonate of lime, vegetable matter, sul- 

 phate of potash. 



Sap of the beech, (FAGTJS sylvatica,) water, acetate of lime, 

 with excess of acid, acetate of potash, gallic acid, tannin, mu- 

 cous extract, acetate of alumine. 



Sap of the Horse Chesnut, (J&scuLvshippocastanum,) water, 

 extractive mucous matter, nitre, acetate of potash, and car- 

 bonate of lime. 



These few examples of the decomposition of vegetable prin- 

 ciples show how wide a field is open to the chemist, in the 

 study of vegetable elements. 



It may seem wonderful, that of so few elementary substan- 

 ces, such a great variety should exist in the taste, smell, colour, 

 consistence, medicinal and nutricious qualities of vegetable 

 combinations ; is it not equally wonderful that, with the nine 

 digits and the cipher, we may make such varied combinations 

 of numbers ; or with our twenty -six letters of the alphabet, form 

 every variety of composition ? Thus, by the various combina- 

 tions of a few simple principles, are formed all vegetable and 

 animal productions ; and, although formerly, the presence of 

 nitrogen was considered as a test of animal substance, and the 

 want of it of a vegetable substance, it is now ascertained that 

 animal substances may exist without nitrogen, and that this 

 principle is contained in several vegetables. 



The elements of the compounds being the same, the question 

 naturally arises, what causes the great diversity in the proper- 

 ties ? Two causes may be assigned for this ; viz. 1st. The 

 * Vauqnelin. 



Sap Of the elm Of the beech Of the horse chesnut All vegetable and 

 animal productions composed of a few simple principles Illustration What 

 two causes assigned for the different properties of compounds formed from 

 the same elements? 



14* 



