FIEST DISCO VEKIES. 27 



time that it is easy to explain why all trace of dis- 

 symmetry disappears when substances which, like rock 

 crystal, have an external dissymmetry are subjected 

 to the process of solution. 



An apparent contradiction to this law of demarca- 

 tion between artificial products and those of animal 

 and vegetable life is presented by the existence in 

 living creatures of substances like oxalic acid, formic 

 acid, urea, uric acid, creatine, &c. None of these pro- 

 ducts exert an action on polarised light or show any 

 dissymmetry in the form of their crystals. But it is 

 necessary to observe that these products are the result 

 of secondary actions. Their formation is evidently 

 governed by the laws which determine the constitu- 

 tion of the artificial products of our laboratories, or of 

 the mineral kingdom properly so called. In living 

 beings they are the products of excretion rather than 

 substances essential to vegetable or animal life. 

 When, on the other hand, we consider the most 

 primordial substances of vegetables and animals 

 those whereof it may be justly said that they are born 

 under the directive influence of becoming life, such as 

 cellulose, fecula, albumen, fibrine, &c. they are found 

 to possess the power of acting on polarised light, a 

 characteristic necessary and sufficient to establish 

 their internal dissymmetry, even when, through the 

 absence of crystallising power, they fail to manifest 

 this dissymmetry outwardly. 



