110 PROCEEDINGS OF THE AMERICAN ACADEMY 



" The following investigation, carried on in the laboratory of the 

 Lawrence Scientific School, at the suggestion of Professor Horsford 

 and under his direction, had for its object the determination of the 

 nutritive values of the several kinds of prepared vegetable food found 

 in our markets, particularly those allied in constitution to the starches, 

 and is based on the amount of nitrogen contained in each. It is a 

 well-known fact in physiological chemistry, that food to be nutritious 

 must contain the ingredients necessary for the formation of the tissues 

 and bones, as well as for the production of heat and formation of fat. 

 The elements of which the tissues are formed are constantly under- 

 going changes, and the matter which at one time sustains vital activity 

 is excreted, and replaced by new matter derived by means of the blood 

 from the food. It is therefore necessary that food should contain the 

 same substances or elements which are found in the different parts of 

 the animal frame. These are carbon, hydrogen, oxygen, nitrogen, 

 sulphur, phosphorus, and some inorganic bases and salts. It is evident 

 at a glance that they may be divided immediately into two classes, 

 organic and inorganic. It is with the former class that we have chiefly 

 to deal in the following pages. The organic class may be subdivided 

 into bodies containing nitrogen, — with which are commonly associated, 

 besides carbon, hydrogen, and oxygen, small quantities of sulphur and 

 phosphorus, — and bodies containing no nitrogen, and conforming near- 

 ly to the formula of starch, Cja H,o Oiq. We have thus divided the ele- 

 ments composing the animal frame, and consequently the elements of 

 food, into three classes, each of which plays its individual part in the 

 animal organism ; — 1st. Bodies containing nitrogen, nitrogenous in- 

 gredients of food ; such are albumen, gluten, &c. 2d. Non-nitrogen- 

 ous bodies, starch, sugar, &c. 3d. Inorganic salts. These, as is well 

 known, are of use in the following manner. The nitrogenous bodies 

 enter into the composition of the tissues. Those containing no nitro- 

 gen contribute to form fat, and from their solution in the blood produce 

 heat, their carbon being gradually burned by means of the oxygen 

 inhaled by the lungs. Lastly, the inorganic salts assist in forming the 

 bones, and enter into the composition of every organ of the body. 

 Their values for the first-mentioned purpose have been the object of 

 the following determinations. 



" In regard to the specimens analyzed, they were taken in the market- 

 able condition, and as it is often the case that tapioca, sago, and arrow- 

 root are largely adulterated, care was taken to procure them of as 



