CONTROLLING FACTORS 227 



ligaments. It also affects the habits of the future progeny, 

 their capacity for consuming feed, and indirectly their power of 

 reproduction. 



Disease is both directly and indirectly transmitted. In the 

 former case diseases which attack the reproductive organs, such 

 as white diarrhoea, are directly transmitted through the egg to 

 the resulting offspring. In other instances diseases, such as tuber- 

 culosis and cholera, by affecting the parent tend to generate in 

 the progeny a weakness of that organ or group of organs which 

 makes the offspring more susceptible to the infection of that par- 

 ticular disease. The specific germs of such diseases are not in- 

 herited, yet the predisposition is. It is this factor of inheritance 

 which marks out an orderly and progressive path for the develop- 

 ment of poultry breeding, and enables the fancier and utility 

 breeders to show every year a systematic advance in the methods 

 of mating their best birds. 



Environment. From the time the egg is laid it is susceptible 

 to external conditions, such as temperature, moisture, and physical 

 changes. These factors are entirely different from the group pre- 

 viously mentioned, as they can be directly influenced or regulated 

 by man. If the embryo is to develop normally and regularly during 

 the incubation period, and the chick be successfully hatched, these 

 external factors of temperature, moisture, and purity of air, as well 

 as certain physical changes, must all be regulated or borne in mind. 



The external conditions, such as shelter and feed, which exist 

 immediately after hatching, influence to a great extent the charac- 

 teristics of the progeny at maturity, and they affect indirectly the 

 future breeding possibilities of the individual. 



All the problems of environment can be most safely solved by 

 planning everything with a view to the comfort of the birds ; other- 

 wise, their growth will not be satisfactory, nor can they be expected 

 to produce a profitable quantity of eggs. 



Cleanliness and sanitary surroundings are very essential, as 

 they tend to minimize the danger of communicable diseases and 

 create an atmosphere of contentment. 



Maintenance of favorable environment is very important during 

 the brooding and rearing period, for a low brooder temperature 

 will chill the young and cause crowding, which will result in weakly 

 developed chicks, if not in their immediate death. Later, during 

 the growing period and when on the range, they need a large area 

 of shade, and an abundance of nourishment, including green feed, 



