PNEUMONIA. 33 



of the lung will float on being placed in water, the condition 

 is known as splenization. 



'2ncl. 'Red hepatization' is the term applied to the second 

 stage. At this time the lung-substance has undergone a 

 more or less destructive process, and will readily sink on 

 being placed in water, its weight having largely increased 

 as the exudate became solidified. In case the patient 

 recovers after the disease has attained this stage, the exu- 

 date is removed after liquifying by the process of absorp- 

 tion, and the lung gradually regains its former condition. 

 At this stage the lung, on being cut into, presents a much 

 redder colour than that of the healthy lung. 



'^rd. ' Grey hepatization ' is the term applied to the third 

 stage of pneumonia, in contradistinction to ' red hepatiza- 

 tion '; but I cannot say that the difference of colour is very 

 well marked ; and as infiltration of pus and fibrin takes 

 place, probably 'purulent infiltration' would be a better 

 term by which to designate the third stage of pneumonia. 

 When this stage is reached, death is the usual result. The 

 diseased spot may be circumscribed, and not spread. This 

 is particularly common in pleuro-pneumonia of the ox. The 

 various stages are uncertain as to duration, engorgement in 

 some cases lasting for a very brief period, and terminating 

 in hepatization. Pneumonia may justly be described as a 

 very insidious disease, frecj[uently proceeding to a very great 

 extent without showing many signs of its presence. 



Causes. — Among the causes may be enumerated the fol- 

 lowing : exposure to cold and dampness, standing in a 

 draught, neglected catarrh. An animal suff'ering from a 

 case of simple catarrh, on being put to work, will often 

 develop a case of pneumonia. It may occur as a result of 

 some irritant substance, as medicine, gaining access to the 

 lungs, inhalation of smoke, badly ventilated stables. It is also 

 due occasionally to the presence of some morbific influence 



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