ANIMAL PRODUCTIOX. 265 



'•An extended survey of the literature of food supply and the food habits 

 of many races makes it plain that in no country is there a greater variety of 

 readily accessible foods of good quality than in the United States and in none 

 is there a more general use of a wide range of articles. Thanks to our varied 

 climate, our ready means of transportation, and our facilities for marketing 

 and handling food products, the contributions of any given locality are readily 

 accessible in other regions. Skill in selecting from this great variety of food 

 products and in the preparation of foods after they are purchased is essential 

 if out of our abundance a diet is to be secured which is best suited to the 

 needs of the American ijeople. The dietary studies herein summarizetl and other 

 similar reliable data seem to show that the people of the T'nited States as a 

 whole are adequately nourished as compared with other races. The acknowl- 

 edged energy and achievement of the American people, together with their gen- 

 eral good health and physical well being, certainly indicate that we have in 

 the main used our food resources advantageously." 



ANIMAL PRODUCTION. 



Chemical studies on growth. I, The inverting enzyms of the alimentary 

 tract, especially in the embryo, L. P.. Mendel and P. H. Mitchell (Amcr. 

 Jour. riiysioL, 20 (1908), Xo. 1, pp. 81-96). — The conclusions drawn from the 

 authors" Investigations with pigs, dogs, and chickens follow : 



" The early appearance of inverting enzyms in the intestine of the embryo 

 corresponds with the relatively early specialization, and histological develop- 

 ment of the portion of the alimentary tract here investigated. The alimentary 

 Itroteolytic euzjms, like the sj^ecial glands which elaborate them, come into 

 evidence at a comparatively late period. Maltase is the most universally dis- 

 tributed of all inverting enzyms. In the embryo pig maltase and lactase are 

 found in the intestine, while sucrase is missing. After birth all three enzyms 

 are present. In the full-grown pig lactase is not regularly found in all por- 

 tions of the small intestine. In the newly born puppy all the enzyms are found. 



■■ In birds other conditions prevail. Lactase is not found at any period ; su- 

 crase, on the other hand, is uniformly present in the newly hatchetl chick and 

 the adult hen. One might be inclined toward a teleological explanation for the 

 absence of lactase fi"om the intestine of uonmammalian animals, and similarly 

 for the absence of sucrase fi'om the embryos of the pig. sheep, and cattle. Such 

 considerations apply with less force, however, to the subseciuent formation of 

 sucrase, or its embryonic occurrence in birds. For the px*eseut, the statistics 

 of the occurrence of the alimentary inverting enzyms must await a more ade- 

 quate interpretation with respect to their functional significance. At any rate, 

 it is safe to conclude tha.t the alimentary tract of the young mammal is, as a 

 rule, even more adequately equipped to digest and utilize the sugar of the 

 milk than are the adults of the same species." 



Chemical studies on growth, II, The enzyms involved in purin metab- 

 olism in the embryo, L. P>. Mendel and P, H. Mitchell {Ainer. Jour. PJu/sioI., 

 20 (UiijJS), Xo. 1, pp. 97-116). — The authors summarize the results of their 

 investigations as follows : 



" The nucleic acid of the liver of the embryo pig probably contains only two 

 purin complexes — adenin and guanin. 



" The liver is capable of undergoing autolytic changes at an early age. Nucle- 

 ases are present which liberate puriu bases from the nucleic acid complexes. 



