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, 
