338 CHEMISTRY. 



that on which the Israelites were fed in passing through 

 the wilderness. But this opinion is obviously incorrect, 

 and is not generally received. Besides the want of cor- 

 respondence in taste, general appearance, etc., there is 

 a chemical difference indicated in the following passage 

 from Exodus : " And Moses said, Let no man leave of it 

 till the morning. Notwithstanding they harkened not 

 unto Moses; but some of them left of it till the morn- 

 ing, and it bred worms and stank: and Moses was wroth 

 with them." No such change as this occurs in the man- 

 na now obtained near Mount Sinai, and it shows, therefore, 

 that the manna which was furnished miraculously to the 

 millions of Israelites was of a different chemical compo- 

 sition. 



467. Gluten. The constituents of plants thus far noticed 

 are composed of carbon, oxygen, and hydrogen. But these 

 alone could not sustain and nourish animals, for there is no 

 nitrogen in them. There are other constituents, therefore, 

 which contain this element, in addition to the three of 

 which sugar and starch are composed. The principal of 

 these is gluten, so called because it is a glutinous or sticky 

 substance like glue. You will recollect that in the process 

 of obtaining starch from wheat flour a substance was left 

 on the cloth. This was gluten. It is this in the flour 

 which gives cohesion to bread. Without this the bread 

 would crumble to pieces, for the cells in it, if made of 

 starch alone, would be easily broken down. Though glu- 

 ten is so important a part of grains as food for man and 

 animals, it bears but a small proportion to the starch. In 

 the bread that we commonly eat wheat bread there is 

 about eight times as much starch as gluten. Gluten is 

 analogous to a substance largely existing in animals called 

 fibrin, and for this reason it is often denominated vegetable 

 fibrin. 



