IN THE VEGETABLE KINGDOM. 187 



all the plants existing on the earth's surface with the nitrogen 

 requisite for their growth and perfect development. Ammonia 

 has also been found in every kind of water occurring on the sur- 

 face of the soil, in sea-water as well as in running springs, and 

 has been extracted from the greatest depths of the earth ; as, for 

 instance, with boracic acid from Castel Nuovo, Cherchiago, and 

 other volcanic districts. 



Animals, when they have ceased growing, restore to the outer 

 world nearly all the nitrogen which they take up with nitrogenous 

 substances, and the very exact determinations of Boussingault and 

 several other inquirers show that the quantity of nitrogen given 

 off from the animal organism after the termination of growth 

 equals that which is introduced, and that the amount of nitrogen 

 present in full-grown animals varies only very slightly. Am- 

 moniacal gas is given off directly during respiration ; nitrogenous 

 matters are also far more abundant in the fluid than the solid 

 excrements, and they very readily become decomposed into 

 ammoniacal combinations. 



The reason of the beneficial effects of gypsum and of burnt 

 clay as a manure has not hitherto been very clearly explained ; 

 but Liebig is certainly quite correct in referring it to the property 

 possessed by these substances of fixing ammonia. The gypsum 

 undergoes decomposition with the carbonate of ammonia in the 

 atmosphere, forming sulphate of ammonia, which does not evapo- 

 rate with the same rapidity as the carbonate. It has been long 

 known that alumina and oxide of iron possess the property of 

 absorbing ammonia. This same property of absorbing ammonia 

 is observed in the case of powdered charcoal and decaying wood, 

 the former of which condenses 90 volumes, and the latter 72 

 volumes of this substance. Mulder includes amongst the sub- 

 stances which fix the ammonia in a rich soil, the five acids which 

 he discovered in the humus, namely, ulmic, humic, geic, crenic, 

 and apocrenic acids. These acids, which are formed during the 

 decay of animal as well as vegetable substances, decompose, 

 according to Mulder's view, the carbonate of ammonia which is 

 conveyed to the soil by rain, and, having thus become soluble, are 

 transferred, in the form of ammoniacal salts, to the roots of plants, 

 where they are very rapidly decomposed (even in the extreme 

 ends of the root-fibrils), and are converted into other bodies. 



Fresenius* found, on an average; 0*133 parts of ammonia in a 

 million parts (by weight) of air. Now, if we adopt Marchand's 

 * Ann. d. Ch. u. Pharra. Bd. 64, S. 101 -100. 



