NUTRITION 71 



The plant operates more economically. From the simpler 

 compounds formed by breaking down a highly complex or- 

 ganic nitrogen compound, the plant reconstructs, with the 

 necessary additions, complex compounds of the same or 

 similar sorts. In green plants there is nothing correspond- 

 ing with the excretion of urea by higher animals, and the 

 view long held that asparagin and other amides retained 

 within the plant-body are useless substances, like the ex- 

 crementitious matters cast off by higher animals, has been 

 shown to be false. Although the amides are undoubtedly 

 formed in plants in consequence of the breaking down of 

 proteid compounds, they must be regarded as also represent- 

 ing one stage in' the syntheses of proteids,* The greater 

 economy of plants consists in their being able to use the 

 amides, and probabty also other and simpler substances, 

 formed during the destruction of the molecules of proteids, 

 whereas animals are obliged to cast off large quantities of 

 highly elaborated nitrogenous substances, f 



By means and through progressive syntheses not defi- 

 nitely known, and not necessarily the same in plants of 

 different species, the inorganic nitrogen compounds (ni- 

 trates ) occurring in soil and in water are elaborated, in the 

 body of the plant, to complex compounds containing car- 

 bon, hydrogen, oxygen, and nitrogen. Amides, of which 

 asparagin (C^HgN^O,,) is the most familiar, are gradually 

 built up from nitrates, ammonia compounds, etc., in the 

 plant-body. The amides are soluble, diffusible foods; they 

 may be moved from part to part of the plant as needed, 

 and used in the synthesis of more complex organic nitro- 

 genous compounds, the proteids, etc. Phosphorus and sul- 

 phur are subsequently added to these complex nitrogenous 

 compounds. Substances finally are formed which possess 

 the same physical and chemical structure and properties as 

 those composing the living protoplasm. 

 The incorporation of these final compounds, which are at 



* Schulze, E. f her den Umsatz der Eiweisstoffe in der lebenden Pflanze. 

 Zeitschr. f. physiol. Chemie, Bd. 24. 1898. 



t When I was a student in his laboratory, Strasburger once said to me : 

 " Es ist nicht wie im Thierreich. Die Pflanzen machen nie dummes Zeug I " 



