CHAP. III.] COMPOSITION OF ANIMALS AND PLANTS. 21 



To complete the eriumei-ation of the ternary vegetal compounds, 

 we have to mention the fat vegetal bodies, the non-azotised oils, 

 which are also compounds . in complex molecules of carbon, of 

 oxygen, and of hydrogen. 



After the group of ternary organic substances comes a tribe 

 of azotised compounds, wrongly, aiid in virtue of questionable 

 chemical theories, called quaternary bodies. The molecules of 

 these last bodies are, it is true, formed for the most part by 

 atoms of carbon, of oxygen, of hydrogen, and of azote; but almost 

 constantly a certain quantity of sulphur and of phosphorus 

 must be joined to them. These quaternary compounds are the 

 organic substances Iw excellence ; we seek in vain their analogues 

 in the mineral world. They form themselves spontaneously in 

 the texture of living beings ; whereas the ternary compounds 

 spoken of above can be brought into relation with the carburets 

 of hydrogen which connect them with the inorganic world. 



The azotised vegetal substances form two principal groups, — 

 the group of the alkaloids, and that of the albuminoids. The 

 alkaloids are very complex compounds, capable of combining 

 as bases with an acid. These bodies, unimportant as to quantity, 

 are very important as to their physiological or toxical properties; 

 they are quinine, strychnine, morphine, and so on. 



But the substances which, without question, hold the first 

 rank, the compounds essential to vegetal life as well as to 

 animal life, are those which form the group of the albuminoids. 

 We shall see that these substances constitute the nucleus of the 

 vegetal cells, constitute their internal membrane, that they are 

 also found in the liquid filling the cells, in the protoplasm. 

 Among the most impoi-tant of these substances we must name 

 gluten or vegetal fihrine, so abundant in the seeds of the cereals. 

 To it is given as formula, according to the theory of Mulder, 

 10(C«H3iOi2^5) + s. 



In relation to gluten we have to view glittine, an analogous 

 albuminoidal substance ; it is the coagulable principle of the 

 sap of plants. It is likewise called vegetal albumine. 



