392 



Journal of Agricultural Research voi. xviii. No. 7 



notably Drummond/ who reports much difficulty in securing growth of 

 the chicks in confinement. The chicks were troubled with "leg weak- 

 ness" and " ruffled appearance," both of which defects were attributed to 

 the lack of exercise in the open air. Osborne and Mendel ^ report partial 

 success in raising chickens in confinement. Although they also report 

 much difficulty with the chickens on account of "leg weakness," they 

 were successful in raising several birds which seemed to develop quite 

 normally. There are good reasons why it is desirable to use growing 

 chicks in the laboratory to test the biological value of feeds. They 

 represent an entirely different species from that of the rat or the pig, 

 and it is hardly logical to translate the results secured on those animals 

 to a species lower than mammals in the evolutionary scale. The ease 

 with which it is possible to hatch eggs ni an incubator and the rapid rate 

 at which chicks grow and reach maturity, as well as the comparatively 



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Fig. I. — Graph showing the rate of growth of males and females in all lots. 



small amount of feed required, are points in their favor for investigative 

 work. The problem of securing normal growth in confinement has 

 presented the greatest drawback to the successful use of chicks for this 

 purpose. In the work here reported the writers had little difficulty 

 with the disease known as "leg weakness" in the chicks, or with the other 

 troubles usually experienced when rearing chicks in confinement, as 

 reported in the literature. However, serious trouble was experienced 

 from the eighth to twelfth week, when the chicks were developing a heavy 

 growth of plumage. During this time 64 per cent of the total mortality 

 occurred. The immediate cause of mortality was apparently excessive 

 intestinal fermentation. After this critical stage was passed no further 



> Drummond, Jack Cecil, observations upon the growth of young chickens under laboratory 

 CONDITIONS. In Biochem. Jour., v. lo, no. i, p. 77-88, i pi. 1916. 



5 Osborne, Thomas B., and Mendel, Lafayette B. the growth of chickens in confinement 

 Jour. Biol. Chem., v. a, no. 3, p. 433-438, pi- 4-6. 1918. 



In 



