CHAPTER IV 



Problem, Method, and Technique 



The experiments' reported in the following pages were made 

 with about thirty chicks belonging to four different groups. 

 The first and fourth groups, each consisting of ten chicks, were 

 secured from poultry breeders when the chicks were about two 

 days old. The second and third groups were artificially in- 

 cubated in the laboratory. The chicks used were Plymouth 

 Rocks and all except two were of the Barred variety. The two 

 exceptions were White Plymouth Rocks but neither contributes 

 importantly to the final results. Properly caring for the chicks 

 and keeping them healthy was one of the most serious difificulties 

 which had to be overcome. On the whole, the laboratory 

 hatched chicks proved more satisfactory. 



The most common ills seemed to be due chiefly to improper 

 feeding, irregular temperature, and inadequate ventilation. A 

 few individuals of group 3 survived until the weather became 

 warm enough for them to be 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 died. But 

 as soon as the survivors were placed out of doors their physical 

 condition began to improve, and it was possible to do nearly 

 three times the amount of experimental work that could be 

 formerly done. Evidently, the requirements for healthy labora- 

 tory chicks include an abundance of sunlight and fresh air with 

 the necessity of working for a living. 



The disease giving trouble with the first two groups was a 

 type of "leg weakness," so called because the leg joints become 

 enlarged, the toes curl out of shape, the chicks cannot stand, 

 and they move about only with great difhculty. This trouble 

 ultimately carried off nearly all of the birds which did not suc- 

 cumb to bowel disturbances. With one brood it was probably 

 the result of excessive heat in the hover. 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 



