B.— CHEMISTRY, 53 



in animals and plants. Instead of being the chemistry of organised 

 beings, organic chemistry became the chemistry of carbon compounds. 

 Until the present century the proportion of chemists who, like Scheele, 

 were interested in natural products steadily declined, and biology became 

 of little interest to chemists as a whole, but physiologists have more and 

 more realised the importance of chemistry for their subject and the 

 intermediate subject of biochemistry has rapidly developed. 



The systematic study of natural products, inaugurated by Scheele, 

 was at first continued most successfully in France, by Fourcroy, Vauquelin, 

 and their pupils. Both were at the Jardin des Plantes, and Vauquelin 

 was afterwards at the Faculte de Modecine. Conjointly they discovered 

 urea and hippuric acid, Vauquelin allantoin and asparagin. In 1800 

 about twenty acids were known, but only one hydrocarbon (ethylene) 

 and one alcohol. 



The knowledge of organic substances slowly increased. Braconnot, 

 a pharmacist and later director of the botanic garden at Nancy, examined 

 plants and discovered substances such as salicin and ellagic acid, of no 

 particular importance to physiology, but also obtained glucose from 

 cellulose (linen) and ' sucre de gelatine ' or glycine from glue, thus making 

 two fundamental observations in biochemistry. KirchhofE, a German 

 pharmacist, working at St. Petersburg, had already shown in 1811 that 

 glucose is formed from starch, and investigated the process of malting. 

 In 1833 Payen and Persoz discovered the first enzyme diastase and in 

 1827 a medical practitioner of London, W. Prout, better known to chemists 

 in another connection, could say in a paper : ' On the ultimate composi- 

 tion of simple alimentary substances ' that they might be arranged in 

 three classes, ' the saccharine, the oily, and the albuminous.' 



Thus, quite early, pharmacists and physicians brought organic 

 chemistry into close relation with biology, but further advance could not 

 take place without the development of organic analysis, by Gay-Lussac 

 and Thenard (1810), by Berzelius, Liebig, and others. At first the 

 difficulties were enormous. In 1814 Berzelius wrote to BerthoUet : 

 ' J'ai employe un travail de 12 mois a I'analyse de seulement 14 substances 

 vegetales.' But by analysis Gay-Lussac was able to establish the funda- 

 mental equation for the fermentation of glucose into alcohol and carbon 

 dioxide, and the first systematic advance in biochemistry, also due to 

 analysis, was Chevreul's great work on the fats. Chevreul doubtless 

 acquired an interest in natural substances from his teacher Vauquelin ; 

 he was attracted to the study of fats by the accidental crystallisation of 

 a potassium soap from hydrolysed lard. He altogether isolated seven 

 fatty acids and discovered cholesterol and cetyl alcohol. In his ' Analyse 

 organique,' published in 1824, he already considered as contrary to the 

 spirit of science the assumption that animal and vegetable substances 

 could not be produced artificially. In that very year, 1824, Wohler 

 obtained oxalic acid from cyanogen, the first synthesis of a vital product, 

 if we except Scheele's production of cyanides from carbon, potassium 

 carbonate, and ammonium chloride. Four years later, in 1828, Wohler's 

 synthesis of urea attracted universal attention, and since then much 

 labour has been expended on the synthesis of vital products as an ultimate 

 proof of their structure. 



