292 NATURAL HISTORY OF ORGANIZED BODIES. 



It belonged to BertLelot to overtlirow these erroneous opinions, and to show 

 that the same laws prevail in organic chemistry and mineral chemistry ; to prove 

 that by employing the inorganic elements disclosed by analysis, it is practicable 

 to reproduce by synthesis a great number of the substances found in vegetables. 

 It was thus that, by means of carbon and hydrogen, our learned chemist formed 

 acetylene, C^H^j this body, treated with nascent hydrogen, gave him olefiant 

 gas, C*H*. 



By the employment of water and carbonic acid, Berthelot formed the oxide 

 of carbon, C^O^. This again, by the fixation of the elements of the water, 

 yielded formic acid, C^H^O^, whence w'as obtained the gas of the marshes, C^H'*. 

 From the gas of the marshes, in turn, are derived, by successive condensation 

 of the elements, acetylene, propylene, benzine, and naphtaline. The ternary 

 bodies spring from the preceding by the addition of oxygen. Thus are produced 

 the alcohols: the methylic alcohol, C^H'*0^, by the oxydation of the gas of the 

 marshes; common alcohol, C''H''0^, by the hydratation of the olefiant gas. By 

 removing the hydrogen from the alcohols, we obtain the aldehydes; by oxydizing 

 the alcohols, we forai the organic a(;ids. By the fixation of the nitrogen in these 

 new products, whether by means of anmionia or l)y the action of nitrous acid, 

 we obtain the cpiaternary compounds. So that it may be foreseen that a resort 

 to synthesis will enable us to reproduce artificially those important substances 

 which are called the alcaloids of vegetables. 



The physicist also makes extensive use of synthesis. Thus, when he wishes to 

 produce witli great intensity a phenomenon of wliich analysis has revealed to him 

 the conditions of existence, he constructs an apparatus in which he assembles 

 those conditions, and evokes the phenomenon with a degree of evidence ♦hich 

 leaves no longer any doubt. Knowing, for instance, the electric phenomena 

 which occur between two different metals, both submitted to a chemical action, 

 physicists liave constructed batteries which produce cun-ents of dynamic elec- 

 tricity of a surprising intensity. In general, what is called an instrument of 

 demonstration is constructed in virtue of a synthetic idea. 



In biology, synthesis is generally too little employed, and yet it would appear, 

 in certain cases, eminently useful, whether for controlling the results obtained 

 by analysis or for furnishing a clear and striking demonstration of the phenom- 

 ena. This means of control and demonstration should certainly not be neglected. 

 It is often proper that experiments should be made with the view of reproducing 

 a jihenomenon, and demonstrating that it takes place in certain deternuned con- 

 ditions. In this case, the experimentation is synthetic. One of the principal 

 applications of this method consists in reproducing, outside of the living being, 

 certain phenomena which take place in the interior of the organism. Thus, in 

 order to demonstrate the action which the air exerts on the blood through the 

 walls of the pulmonary cellules, we make it appear that venous blood can be 

 arterialized by the action of the air taking effect through an organic membrane. 

 To prove the action of the acids of the stomach as well as that of heat in diges- 

 tion, it is usual to show that, in a matras, the addition of an acid to a mixture 

 of gastric juice and food excites an artificial digestion which would take place 

 but very incompletely without the presence of the acid. The action of heat in 

 digestion may at the same time be shown, for the temperature must be somewhat 

 elevated for that phenomenon to be produced with rapidity. 



The physical phenomena which occiu' in living beings are particularly sus- 

 ceptible of synthetic demonstration. The apparatus of demonstration or scliemas 

 are admirably adapted to give an idea of the mechanism of these functions; 

 nor can anything more instructive be readily imagined than the employment of 

 such expedients, which enable us to assist, as it Avere, in the production of all 

 the details of the phenomena. 



There are ii\any, doubtless, Avho will recall the difficulties experienced, at the 

 outset of physiological studies, in comprehending })erfectly the mechanism of 



