SECT. XXIV. THE PROPER JUICE. 46l 



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 connected by small 

 and prism-shaped substances placed between them.* 



If this juice could be obtained in a state of purity, Properties, 

 its analysis would throw a considerable degree of 

 light upon the subject of vegetation. But it seems 

 impracticable to extract it without a mixture of sap. 

 Senebier analysed the milky juice of Euphorbia 

 Cyparissias, of which he had procured a small 

 quantity considerably pure, though its pungency 

 was so great as to occasion 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 

 precipitation ensued ; and when allowed to evaporate 

 a thin and opaque crust remained behind. Alcohol 

 coagulated it into small globules. Ether dissolved 

 it entirely, as did also oil of turpentine. Sulphuric 

 acid changed its colour to black ; nitric acid to 

 green. -j~ The most accurate experiments on the 

 subject are those of Chaptal. When oxymuriatic 

 acid was poured into the peculiar juice of Euphor- 

 bia, a very copious white precipitate fell down, 

 which when washed and dried had the appearance 

 of starch, and was not altered by keeping. Alcohol, 

 aided by heat, dissolved two thirds of it, which the 

 Phys. Veg. vol. ii. p. 3fa, f Ibid. P- 3$5 



