HOUSING AND HYGIENE 



295 



weather, and quickly sap the vitahty of the stock and 

 often cause death. In order to eradicate them it is always 

 necessary to spray twice and often three times. 



Most of tlie commercial coal-tar dips kill the mites, but 

 it is difficult to make them penetrate far enough into the 

 cracks between the boards to reach and destroy the eggs. 

 The result is that a new generation soon appears. It is 

 necessary to spray again in order to destroy these. The 

 period between sprayings is governed by the prevailing 

 temperature. If it is very warm the second spraying should 

 follow the first in five to seven days. If it is rather cool, 

 ten days will be al)out right. 



Fig. 107 



An excellent type of permanent poultry-house. Note the box for saving 

 the droppings at the right end of the building. (Courtesy of Purdue xAgri- 

 cultural Experiment Station.) 



Value and Preservation of Poultry Manure. — With reference 

 to conserving the value of the fertility in the droppings, 

 Purvis' quotes the New Hampshire Experiment Station as 

 saying: "As is well known, when poultry droppings accu- 

 mulate under the roosts and when they are left in barrels 

 there is a strong odor of ammonia noticeable. The develop- 

 ment of such an odor is a sure sign that gaseous ammonia 

 is escaping into the air, to be lost for the present." Several 



Pnultr\' Breeding 



