Diseases of the Respiratory System 171 



and requires accuracy and careful manipulation, but after 

 one becomes accustomed to it he can standardize by the tur- 

 bidity of the vaccine with enough accuracy to be correct as 

 is needed to be used on chickens. The turbidity may be 

 compared to that of two drops of milk in ten cubic centi- 

 meters of distilled water. 



"The average dose is one cubic centimeter given sub- 

 cutaneously with a hypodermic syringe. The most con- 

 venient place to inject the vaccine is under the skin over the 

 region of the breast. This need not be repeated in immuniz- 

 ing healthy birds, but in treating sick birds a second or third 

 injection may be necessary every five days." 



This method of treatment is not yet on a secure scientific 

 basis and it cannot be used in practice by the poultryman or 

 farmer until all doubt of its efficiency is removed and a 

 reliable vaccine prepared and put on the market. If this is 

 ever accomplished, treatment with vaccine will be much 

 cheaper to administer and much more efficient than the local 

 disinfection of lesions. 



Prognosis. — In very acute cases death may occur in two 

 or three days. More often even in fatal cases the disease 

 runs for two or three weeks. Recovery may be complete in 

 two or three weeks or an individual may develop a chronic 

 form of the disease which continues for several months. If 

 untreated 'about half of the birds which contract the disease 

 die. 



Pip {Inflammation of the Mouth) 



The term "pip" as used by poultrymen evidently does not 

 represent a separate disease but is the result of mouth breath- 

 ing due to closure of the nostrils by cold or catarrh. The 

 mucous membrane of the mouth and tongue become hard and 

 dry. This is especially true at the end of the tongue. Mucous 

 discharge from the mouth often collects and dries on to this 



