VARIABLE QUANTITIES OF GLUTEN IN WHEAT. 95 



the Bavarian contained 24 per cent. ; Davy obtained 

 19 per cent, from winter, and 24 from summer 

 wheat; from Sicilian 21, and from Barbary wheat 

 19 per cent. The meal of Alsace wheat contains, 

 according to Boussingault, 17*3 per cent, of gluten; 

 that of wheat grown in the " Jardin des Plantes " 

 26-7, and that of winter wheat 3*33 per cent. Such 

 great differences must be owing to some cause, and 

 this we find in the different methods of cultivation. 

 An increase of animal manure gives rise not only 

 to an increase in the number of seeds, but also to 

 a most remarkable difference in the proportion of 

 the substances containing nitrogen, such as the 

 gluten which they contain. 



Animal manure, in as far as regards the assimila- 

 tion of nitrogen, acts only by the formation of am- 

 monia. One hundred parts of wheat grown on a 

 soil manured with cow-dung (a manure containing 

 the smallest quantity of nitrogen), afforded only 

 11-95 parts of gluten, and 64*34 parts of amylin, or 

 starch; whilst the same quantity, grown on a soil 

 manured with human urine, yielded the maximum of 

 gluten, namely 35*1 per cent. Putrefied urine con- 

 tains nitrogen in the forms of carbonate, phosphate, 

 and lactate of ammonia, and in no other form than 

 that of ammoniacal salts. 



" Putrid urine is employed in Flanders as a ma- 

 nure with the best results. During the putrefaction 

 of urine, ammoniacal salts are formed in large quan- 

 tity, it may be said exclusively; for under the in- 

 fluence of heat and moisture, urea, the most promi- 

 nent ingredient of the urine, is converted into car- 

 bonate of ammonia. The barren soil on the coast 

 of Peru is rendered fertile by means of a manure 

 called Guano, which is collected from several islands 

 in the South Sea.^ It is sufficient to add a small 

 quantity of guano to a soil, which consists only of 



* The guano, which forms a stratum several feet in thickness upon 

 the surface of these islands, consists of the putrid excrements of in- 



