OF BREAD. 



33 



Variations in the composition of milk from its normal standard are ob- 

 served to depend upon age and bodily health. Young fe- influence of 

 males, from fifteen to twenty, yield a milk more rich in sol- ?&!!& 

 ids than that which is given at thirty-five or forty. Gesta- sition of milk. 

 tion at a late period increases the solid portions. The following table 

 of Vernois and Becquerel illustrates the influence of disease : 







Influence of Disease on the Constitution of Milk. 



From this consideration of the nature and properties of the food of in- 

 fancy, we may pass to the examination of that of the mature period. 



Experience has shown that, of all articles of food, bread made from 

 wheaten flour meets best the requirements of the adult life of 



T, ^ 11 ,1 , f A Of bread. 



man. It seems to contain all that is necessary lor support. A 



very simple analysis will show how it presents both the respiratory and 



nutritive elements. 



If such flour be made into a paste with water, and be gradually washed 

 with a larger quantity, an elastic coherent mass is left, and Examination 

 the water assumes a milky turbidity. After a time it be- ^atandof 

 comes clear, through the settling of a white precipitate, which other grains. 

 is starch, the leading member of the respiratory group. The elastic sub- 

 stance is gluten, which is a true vegetable fibrin, mixed with another 

 nitrogenized body, gliadine, which may be removed, along with a certain 

 quantity of oil, by washing with ether and alcohol. 



Thus, simply by washing in water, flour may be separated into two 

 physiological elements, respiratory and nutritive, the former being the 

 starch, and the latter the gluten. The relative quantity of tlicse substan- 

 ces differs in different samples of flour, and, other things being equal, the 

 greater the amount of gluten the more valuable the sample, because the 

 more nutritious. It is interesting to remark that the liquid from which 

 the starch has settled, if brought to the boiling pointy becomes turbid 

 again, from the coagulation of the vegetable albumen it contains. 



Other grains, treated in the same manner, yield similar results. The 

 flour of barley and of the oat, when washed with water, do not, however, 

 yield gluten, but a pure fibrin, with a separation of starch. 



The fibrin occurring in these grains is replaced in other nutritious 

 seeds, such as peas and beans, by legumin, which, like the casein of milk, 

 does not coagulate by boiling, but merely forms tenacious skins as it is 

 evaporated. These may be removed by skimming. This substance, 



C 



