CHAP. lii.] COMPOSITION OF ANIMALS AND PLANTS. 25 



Heating in suitable conditions this body with potash or 

 hydrate of potassium, we detei-mine the displacement of the 

 atom of iode, which combines with the potassium and is suc- 

 ceeded by the oxygen of the potash. But this oxygen is di- 

 atomic : the half only of its affinity is satisfied or neutralised by 

 this displacement : the rest still remains free. This is why, 

 without ceasing to form part of the ca'rburet, the atom of 

 oxygen unites itself on its own account with a molecule of 

 hydrogen likewise taken from the hydrate of potassiimi, and we 

 have thus wood spirit : 



H 



H— C— (OH) 



H 



We have taken as example a body in which one atom only 

 of carbon figure's. But if we represent to ourselves a poly-car- 

 bonised compound we at once see to what a degree of complexity 

 and mobility such a body can attain ; therefrom we gain a general 

 idea of what the chemistry of organic bodies is ; we recognise 

 that modem chemists have the right to call this branch of their 

 science the chemistry of the compounds of carbon ; and we 

 willingly subscribe to this proposition of Haeckel : " It is only 

 in the special chemico-physical properties of carbon, and 

 especially in the semi-fiuidity and instability of the carbonised 

 albuminoidal compounds, that we must seek the mechanical 

 causes of the phenomena of particular movements by which 

 organisms and inorganisms are difierentiated, and which is called 

 in a more restricted sense Life." ^ 



The general statements given above apply equally to organic 



' vegetal substances, and to organic animal substances, forasmuch 



as we have seen that as regards quality, as regards general 



^ E. Haeckel, Histdre de la Creation Natv/relle. Paris, 1874. 



