SIZE AND FORM PERCEPTION 77 



poultry breeder when the chicks were about two days old. The 

 second and third groups were artificially incubated in the labo- 

 ratory. All of the chicks used were of the Barred Plymouth 

 Rock variety. The matter of caring for the birds and keeping 

 them healthy was one of the most serious difficulties which I 

 had to overcome. On the whole, I found it more satisfactory 

 to use the laboratory hatched chicks. 



The most common ills were bowel trouble and "leg weak- 

 ness." Both types of disease were chiefly due to improper 

 feeding, temperature, and ventilation. My experience leads me 

 to conclude that chicks in close confinement must be fed on 

 "starving rations." A few individuals of group 3 survived until 

 the weather became warm enough to get them out of doors 

 during a few hours on favorable days. When this plan was 

 first tried the birds were in poor condition. Two-thirds of the 

 group had already died. But as soon as the survivors were 

 placed out of doors their physical condition began to improve, 

 and I was able to do nearly three times the amount of experi- 

 mental work that I could formerly accomplish. Apparently 

 the factors that healthy laboratory chicks require is an abun- 

 dance of sunlight and fresh air with an opportunity to work 

 for their living. 



The "leg weakness" is a type of disease which had previously 

 given trouble in the laboratory. The leg joints become enlarged, 

 the toes curl out of shape, the birds cannot stand, and they 

 move about only with great difficulty. This trouble ultimately 

 carried off nearly all of the birds which did not succumb to 

 bowel trouble. In the case of one brood I think it was the 

 result of excessive heat in the brooder. In other cases it was 

 probably due to overfeeding. More often, perhaps, it was due 

 to a combination of both conditions. The birds which first 

 showed signs of this weakness were the largest and apparently 

 strongest of the flock. There was no evidence of it among the 

 chicks of the third group, which were fed very sparingly, while 

 the temperature of the brooder was carefully regulated. 



2. The problem 



The matter of health among the chicks turned out to be a 

 problem which had not been anticipated. However, it did not 

 prevent work toward the solution of the primary problem. The 



