ANIMAL PRODUCTION. 865 



p. 872), in which rats fed certain mixtures composed of pure casein, carbo- 

 hydrates, and salt mixtui-es made normal growth for periods varying from 70 

 to 120 days, but after that time made little or no increase in the body weight. 

 Fat from egg yolk or butter was added to the ration. Growth was imme- 

 diately resumed. ;When olive oil was added, however, no such effect was pro- 

 duced. The results suggest a difference between the physiological values of fat 

 from different sources. 



Some mechanical factors in digestion, S. SissoN (Amer. Vet. Rev., 45 {1914), 

 Nos. 4, pp. 408-422; 5, pp. 513-526). — This is a rather complete treatise on the 

 mechanical factors involved in digestion by domestic animals, especially horses 

 and cattle. The investigations made by Scheunert, Schattke, and others are 

 cited. 



Controlled natural selection and value marking, J. C. Mottram (London, 

 New York, Bombay, and Calcutta, 1914, pp. IX+ISO, figs. 8). — The author of 

 this book presents a new theory with regard to the course taken by natural 

 selection. He contends that since natural selection must appreciate differences 

 in structure and since it must treat associations as units and bring about di- 

 versity of structure in them these structures control natural selection, so that 

 the less valuable individuals are more liable to be destroyed than the more 

 valuable. It is thought that the application of this theory or hypothesis may 

 explain the origin and use of some polymorphisms. 



Coat color in pointer dogs, C. C. Little {Jour. Heredity, 5 {1914), No. 6, 

 pp. 244-24S). — From a study made of the studbook of the American Kennel 

 Club with reference to coat color in pointer dogs it is concluded that there is a 

 recessive type of yellow dog, analogous to the recessive yellow of guinea pigs, 

 and that the relation of brown to black is the same in dogs as in other small 

 mammals in which the matter has been experimentally investigated. 



Nondisjunction of the sex chromosomes of Drosophila, C. B. Bridges {Jour. 

 Expt. Zool., 15 {1913), No. 4, pp. 587-606; ahs. in Seience, n. ser., 40 {1914), 

 No. 1020, pp. 107-109). — The author of this article presents evidence tending to 

 prove that the parallelism between the behavior of the chromosomes and the 

 behavior of sex-linked genes and sex in the case of Drosophila means that the 

 sex-linked genes are located in and borne by the X-chromosomes. 



Animal industry in the Kongo, E. Leplae {Min. Colon. Belg., Rap. Agr. 

 Congo Beige, 1911-12, pp. 210-244, figs. 29).— This report relates to the types of 

 cattle, horses, mules, sheep, and swine indigenous to the Kongo, their improve^ 

 ment and utility value, and to the importation of foreign breeds into that 

 section. 



Economic factors in cattle feeding. — IV, Cattle feeding conditions in the 

 com belt, H. W. Mumford and L. D. Hall (Illinois Sta. Circ. 175 (1914), pp. 

 5-19, figs. 2). — In this discussion of prevailing conditions, it is stated that 

 about one-third of the cattle of the country other than milch cows are contained 

 in the seven States embracing what is known as the corn belt, and that their 

 value is equal to about two-fifths of the total value of such cattle in the United 

 States. It is shown that the number of beef cattle bred in this section is 

 rapidly diminishing, the supply of feeders coming largely from the West or 

 elsewhere. At the same time there has been an enormous increase in the 

 number of dairy cattle, the indiscriminate breeding of which to beef stock has 

 deteriorated the quality of beef cattle. Four-fifths to nine-tenths of the beef 

 cattle marketed from typical corn-belt localities are cattle that have been 

 purchased as stockers or feeders, while the fattening of cattle has passed 

 largely from the hands of general farmers to those of professional cattle feeders. 



Causes attributed for these conditions are the relatively high prices of grain 

 compared with those for fat cattle, increase in land values, extension of cattle- 



