108 RAPHIDES COMPOSITION. [BOOK i. 



taken up again, are therefore unsuited to the vital exigencies 

 of the vegetable, and probably are of no use, even mechani- 

 cally, in the several tissues which contain them, because plants 

 of many kinds do not secrete such formations : therefore, it 

 will be nearer the truth to regard them, as Link has done, 

 as nothing more than accidental deposits. 



In all the analyses lime has been found the greatest 

 constituent of these bodies : and since this material is so 

 intimately associated both with animal and vegetable organi- 

 sation, as not perhaps to be wanting in any individual of 

 either kingdom, there is every reason for its being so gene- 

 rally the base of such crystals. Moreover, since it is the 

 property of some vegetables to combine, out of their materials 

 of sustenance, varied proportions of oxygen and carbon, 

 which, when apportioned in the ratio of three of the former 

 to two of the latter, form oxalic acid, the presence of that 

 agent in a plant, in contact with lime, can scarcely fail in 

 producing a crystalline substance with it. Again, as phos- 

 phoric acid is a frequent accompaniment of animal and 

 vegetable organisation either introduced with the food, or 

 created out of it, (it being yet a problem to solve how this 

 and other elementary matters are produced,) it can be readily 

 conceived why compounds with it and lime should be formed 

 as well as with the former acid ; because, as the earthy and 

 other matters are absorbed from the moisture of the soil, 

 they must necessarily meet with these acids when they exist, 

 and the vitality of the plant does not prevent their forming 

 the crystals which have been here described ; still there are 

 some curious points connected with their production. If 

 oxalic or phosphoric acid be added to a solution of lime, 

 instead of crystals, a pulverulent opaque precipitate is ob- 

 tained, which does not happen in the interior of the plants : 

 therefore various experiments have been devised, to discover 

 the method of making crystals by combining the above sub- 

 stances. Some have been ineffectual, such as making a 

 plant, which contains lime in its composition, absorb water 

 with a small quantity of oxalate of ammonia dissolved in it : 

 from the want of temperature which would create a necessity 

 or moisture in the plant this experiment failed. A method, 



