292 NATURAL HISTORY OF ORGANIZED BODIES. 



It belonged to Bertliclot to overtlirow tliese erroneous opinions, and to show 

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

 that 1)V 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 bodv, 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^. I'his again, by the fixation of the elements of the water, 

 yielded formic acid, C^H-0^, whence was 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 alcoliol, C^li'*0^, by the oxydation of the gas of the 

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

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

 the alcohols, Ave form the organic acids. By the fixation of the nitrogen in thesti 

 new products, whether by means of ammonia or by the action of nitrous acid, 

 we obtain the quaternary 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 with great intensity a phenomenon of which anah'sis has revealed to him 

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

 those conditions, and evokes the phenomenon Avith a degree of evidence which 

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

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

 physicists have constructed batteries which produce cmTcnts of dynamic elec- 

 tricity of a surprising intensity. In general, Avhat 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, Avhether 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 cei'tainly not be neglected. 

 It is often proper that experiments should be made Avith the Anew of reproducing 

 a phenomenon, and demonstrating that it takes place in certain determined 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 Avhich take place in the interior of the organism. Thus, in 

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

 Avails of the pulmonar}^ cellules, Ave make it appear that A'enous blood can be 

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

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

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

 of gastric juice and food excites an artificial digestion Avhicli Avould take place 

 but very incompletely Avithout the presence of the acid. The action of heat in 

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

 elevated for that phenomenon to be produced Avith rapidity. 



The physical phenomena Avhich occur in living beings are particularly sus- 

 ceptible of synthetic demonstration. The apparatus of demonstration or schemas 

 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, Avhich enable us to assist, as it Avere, in the production of all 

 the details of the phenomena. 



There are many, doubtless, Avho Avill recall the difficulties experienced, at the 

 outset of physiological studies, in comprehending perfectly the mechanism of 



