214 Vetej'inary Medicine. 



inflammation of these tissues and nuclei, with exudatiou usually 

 of a fibrinous material into their substance. 



Predisposing Causes. ^. Age. A very early age is nearly 

 exempt, and from 6 j^ears upward there are fewer cases relative to 

 the equine population, variations that may be bstter accounted for 

 by stabling, training and acquired immunity than by the mere 

 fact of age. Of 237 cases, 2 were 3)^ years ; 32 were 4 years ; 

 19 were 5 years ; 131 were 6 to 11 years ; 46 were over 11 years ; 

 and 7 of uncertain age (Trasbot). 2. Sex. No visible effect. 

 3. Stabling, training, change of food. While the young colt 

 at pasture is practically immune, the period of stabling, transi- 

 tion to a dry and grain diet, and to the nervous excitement at- 

 tendant on training and unwonted work as shown in the statistics 

 of Percivall and Trasbot determine an enormous increase of cases. 

 In a cavalry regiment Percivall found that 56.6 per cent, of all 

 lung diseases occurred before the 5th year, and Trasbot found 

 that at the Alfert Veterinary College 13.5 per cent, of all equine 

 pneumonias occurred in the 4th year. 4 Hot Stables. Impure 

 Air. These two conditions usually coexist and prove potent 

 causes especially in young horses brought from the fields. We 

 cannot, however, separate this cause as usually observed from the 

 action of pathogenic germs which are preserved and concentrated 

 in such places. 5. Poor Health. Debilitating diseases, insuf- 

 ficient and poor diet, overwork, exposure to cold draughts or 

 darkness and any other cause which lowers the vitality predis- 

 poses. 6. A Previous Attack. This usually leaves some struc- 

 tural or functional change which renders the lung more sus- 

 ceptible to a subsequent invasion. Against this must be placed 

 the immunity which follows the contagious forms, but as this is 

 usually exhausted in the course of six months it does not invali- 

 date the position that the permanent impairment of pulmonary in- 

 tegrity is a predisposing cause. 7. Plethora Tending as this 

 does to congestion it must be accepted also for the next patho- 

 logical step — pneumonia. 8. Climate and Season. This is 

 notoriously an important factor. At Paris, Trasbot met with 237 

 cases in the nine months from October to June inclusive and but 

 8 ca.ses in the summer months — July, August and September. In 

 Great Britian, where the vicissitudes are le.ss .severe Percivall had 

 in the cavalry horses in the seven months from October to April 



