VEGETABLE PRODUCTS. 



153 



formation of carbonate of lime and acetate of 

 potass, whicli it previously held in solution. 

 Alkalies combine with it readily, and saturate 

 its excess of acid. They resist its tendency to 

 spontaneous decomposition, and retain in solu- 

 tion its extract. 



Deyeux and Vauquelin instituted a set of ex- 

 periments on the nature of this sap. The former 

 analyzed the sap of the vine and elm, and found 

 in it acetate of lime, acetous acid, and an extract 

 to which he attributed the formation of ammo- 

 nia, and the spontaneous precipitation of the sap 

 when left exposed to the action of the air. But 

 the analysis of Vauquelin was more minute. In 

 the sap of fagus svhatica he found the follow- 

 ing ingredients : Water, acetate of lime, with ex- 

 cess of acid, acetate of potass, gallic acid, tannin, 

 mucous extractive matter, and acetate of alumi- 

 na. In 1039 parts of the sap of ulmus campes- 

 tris, he found 1 .027 parts of water and volatile 

 matter, 9.240 of acetate of potass, 1.060 of veget- 

 able matter, 0.79C of carbonate of lime, besides 

 some slight indications of the presence of sulphu- 

 ric and muriatic acids ; and at a later period of the 

 season he found the vegetable matter increased, 

 and the carbonate oi- lime and acetate of potass 

 diminished. From the above experiments, there- 

 fore, as well as from those of other chemists, it 

 is plain that the sap consists of a great variety 

 of ingredients differing in different species of 

 plants, though there is too little known concern- 

 ing it to warrant the deduction of any general 

 conclusions, as the number of plants whose sap 

 has hitherto been analyzed is yet but very 

 limited. It is the grand and principal source of 

 vegetable aliment, and may be regarded as being 

 somewhat analogous to the blood of animals. It 

 is not made use of by man, at least in its natural 

 state; but there are trees, such as the birch, 

 whose sap may be manufactured into a very 

 pleasant wine ; and it is well known that the sap 

 of the American maple tree yields a considerable 

 quantity of sugar. Boussingault has lately ex- 

 amined the sap of the musa paradisaica. It is 

 limpid like water. When left exposed to the 

 air it lets fall red flakes. It stains linen ; but 

 loses this property by exposure to the air. It 

 contains tannin, gallic acid, acetic acid, common 

 salt, and salts of lime, potash, and alumina. 



The proper juice. After the sap has passed 

 into the leaves, and has thus communicated with 

 the atmosphere, it becomes elaborated into what 

 is called the proper juice, and descends again 

 through the vessels of the stem. This fluid is 

 distinguishable from the sap by a difference of 

 colour, as well as qualities. Thus in the peri- 

 winkle it is green, in logwood red, white in spurge, 

 and yellow in the celandine, from the two last 

 of which it may readily be obtained by breaking 

 the stem asunder, as it will then exude from the 

 fracture. Its principal seat is in the bark, where 



it occupies the simple tubes ; but sometimes it is 

 situated between the bark and wood, as in the 

 juniper tree ; or in the leaf, as in the greater 

 part of herbs ; or it is diffused throughout the 

 whole plant, as in the fir and hemlock, in which 

 case either the proper juice mixes with the sad, 

 or the vessels containing it have ramifications so 

 fine as to be altogether imperceptible. It is not, 

 however, the same in all plants, nor even in the 

 different parts of the same plant. In the cherry 

 it is mucilaginous, in the pine it is resinous, in 

 spurge and celandine it is caustic, though resem- 

 bling in appearance an emulsion. In many 

 plants the proper juice of the bark is different 

 from that of the flower, and the proper juice of 

 the fruit different from both. Its appearance 

 under the microscope, according to Senebier, is 

 that of an assemblage of small globules, con- 

 nected by small and prism-shaped substances 

 placed between them. If this juice could be ob- 

 tained in a state of purity, its analysis would 

 throw considerable light on the subject of vege- 

 tation ; but it seems impracticable to extract it 

 without a mixture of sap. Senebier analyzed 

 the milky juice of euphorbia cyparissus, of which 

 he had procured a small quantity considerably 

 pure, though its pungency was so great as to oc- 

 casion an inflammation of the eyes to the person 

 employed to procure it. It mixed readily with 

 water, to which it communicated its colour. 

 When left exposed to the air a slight precipita- 

 tion ensued ; and when allowed to evaporate, a 

 thin and opaque crust remained behind. Alco- 

 hol coagulated it into small globules. Ether 

 dissolved it entirely, as did also oil of turpen- 

 tine. Sulphuric acid changed its colour to black, 

 nitric acid to green. The most accurate experi- 

 ments on the subject are those of Chaptal. When 

 oxymuriatic acid was poured into the peculiar 

 juice of euphorbia, a very copious white precipi- 

 tate fell down, which, when washed and dried, 

 had the appearance of starch, and was not al- 

 tered by keeping. Alcohol, aided by heat, dis- 

 solved two kinds of it, which the addition of 

 water again precipitated. They had all the pro- 

 perties of resin. The remaining third part pos- 

 sessed the properties of woody fibre. The same 

 experiment was tried on the juice of a variety of 

 other plants, and the result uniformly was, that 

 oxymuriatic acid precipitated them from woody 

 fibre. 



The peculiar qualities and virtues of plants 

 seem to reside in their proper juice. Thus the 

 juice of the poppy is narcotic, furnishing opium. 

 The stimulating and diuretic effects of the fir are 

 in its turpentine. Cinnamon and other aromatic 

 shrubs yield a highly pungent essential oil. The 

 resinous juice of the jalap is a purgative. Sugar 

 is the sweet juice of the sugar cane, the maple 

 tree, and the beet root. The bark of trees con- 

 tains this juice in greatest abundance, as is ex- 

 u 



