VIII. BIOTECHNICS. 



Since plants are modified in appearance and special pro- 

 ducts by the use of manures, and the products of animals are 

 influenced by food and other conditions, the study of these 

 modifying circumstances is an art of the highest importance. 

 To ascertain them to a limited extent, empirical experiment 

 will be of much assistance ; but to determine them more fully, 

 proximate analysis of organized bodies and organic mixtures 

 demands a more thorough elaboration. Quantitative proxi- 

 mate analysis is still in its beginning. After this, or simul- 

 taneous with its development, must be a study of the successive 

 changes experienced by special substances in plants and ani- 

 mals during growth, both in normal and abnormal conditions, 

 under usual circumstances or when subjected to particular 

 chemical influences. We have an ingenious investigation of 

 this kind to report by Fremy. 



1. Physiology. — Ripening of Fruit. — Fremy's investigation 

 of the ripening of fruits has opened a new and interesting field. 

 He calls pectose a substance associated with cellulose in unripe 

 fruits, in carrots, turnips, &c. ; it is insoluble in water, alcohol, 

 and ether. It is converted into pectin by heat and dilute acids, 

 or by the ripening of fruits, in which case malic and citric acids 

 produce the effect. When pectin is boiled for some time in 

 water, it is converted into parapectin, of the same composition 

 as pectin, but precipitable by sugar of lead. Parapectin 

 boiled with dilute acids is rapidly changed to metapectin, of 

 the same composition as pectin, but decidedly acid, and pre- 

 cipitable by chloride of barium. Fremy has found a ferment 

 in fruits, and carrots, &c., which he terms pectas, the soluble 

 modification of which is obtained from carrots. Pectas, or 

 cold dilute alkaline solutions, transforms pectin into pectosio 

 acid. The longer action of pectas, or alkalies, or ebullition 



