246 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1949 
12. Prick, WESTON A. 
1939. Nutrition and physical degeneration. A comparison of primitive 
and modern diets and their effects. 431 pp., illus. Haeber, New 
York. 
13. Rosperts, R. C., et al. 
1942. Soil survey of Puerto Rico. U.S. Dep. Agr., Series 1936, No. 7, 
503 pp., illus., maps. 
14. Roxpinson, W. O., Eppineton, GLEN, and Byers, H. G. 
1935. Chemical studies of infertile soils derived from rocks high in mag- 
nesium and generally high in chromium and nickel. U.S. Dep. 
Agr. Techn. Bull. 471, 28 pp. 
15. Unrrep Srates DEPARTMENT OF AGRICULTURE. 
Reports of investigations at the Soil Conservation Experiment 
Stations. Techn. Bull. 558, 837, 859, 860, 873, 888, and 916. 
