438 CARNEGIE INSTITUTION OF WASHINGTON. 



ture rarely forms the sole diet of young animals, and when, as is gener- 

 ally the case, some green fodder is eaten, this possible deficiency would 

 be provided for. It is possible that the deficiency in mineral matter 

 would also be compensated in this way, but to be on the safe side it 

 would be well to add about 1 pound each of calcium carbonate and 

 sodium chloride per 100 pounds of cornmeal. 



At the request of the officers of the American Medical Association, 

 an exhibit of some chemical features of nutrition was prepared under 

 our direction in cooperation with the Connecticut Agricultural Experi- 

 ment Station for the Boston meeting of the association. It consisted 

 of stuffed experimental animals and photographs and charts illustrating 

 the results of various lines of investigation in which we have been en- 

 gaged. A descriptive leaflet was distributed in connection therewith. 

 The exhibit was awarded a certificate of merit. 



In raising our stock rats we have taken great pains to exclude 

 animals which gave evidence of disease and have regularly eliminated 

 all the young which were under size soon after the period of weaning. 

 The result of this has been to furnish us with an unusually vigorous 

 stock. At the same time the average adult size of our animals, both 

 male and female, has shown a gradual increase, so that the stock colony 

 to-day represents a gi'oup of individuals decidedly heavier in weight 

 than were our stock animals at a corresponding age ten years ago. 

 One male attained a maximum weight of 615 grams at the age of 289 

 days. This surpasses the record for size recorded by Donaldson (The 

 Rat, Philadelphia, 1915). 



In our last report we gave an account of the proteins of the spinach 

 leaf. This was our first attempt to study the proteins of fresh green 

 plants. The methods devised for that investigation have since been 

 applied to alfalfa, a lorage plant of much economic importance. 

 Further experience with these methods has led to improvements 

 whereby it now appears to be possible to learn not only much that is 

 new respecting the proteins of alfalfa, but also respecting its other 

 constituents, about which little is as yet known. 



While very many interesting and important observations have been 

 made concerning the occurrence of a multitude of different substances 

 in plants of many kinds, our present knowledge of the chemical con- 

 stituents of any single green plant is fragmentary. Until a much more 

 comprehensive knowledge of the chemical make-up of some one indi- 

 vidual species is obtained, plant physiology, as well as plant physics, 

 necessarily will rest on an inadequate basis. If the methods described 

 in the followinf pages can be applied successfully to other green plants, 

 it seems probable that before very long much can be learned which will 

 fill this gap in our present knowledge of plant chemistry. 



By using suitable mills and presses it has been possible to obtain 

 relatively large quantities of the undiluted juice of the alfalfa plant and 



