INFECTIOUS DISEASES. 513 



stable in which two cases of influenza had broken out the day before ; 

 in six days the colt developed the disease. On the morning when the 

 trouble in the colt was recognized it stood in an infirmary with a 

 dozen horses that were being treated for various diseases, but was 

 immediately isolated ; within one week two-thirds of the other horses 

 had contracted the disease. 



SymptoTns. — ^After the exposure of a susceptible horse to infection 

 a period of incubation of from four to seven days elapses, during 

 which the animal seems in perfect health, before any symptom is 

 visible. When the symptoms of influenza develop they may be in- 

 tense, or so moderate as to occasion but little alarm, but the latter 

 condition frequently exposes the animal to use and to the danger of 

 the exciting causes of complications which would not have happened 

 had it been left quietly in its stall in' place of being worked or driven 

 out to show to prospective purchasers. The disease may run a 

 simple course as a specific fever, with alterations only of the blood, 

 or at any period it may become complicated by local inflammatory 

 troubles, the gravity of which is augmented by developing in an 

 animal with an impoverished blood, an already irritated, rapid cir- 

 culation, and defective nutritive and reparative functions. 



The first symptoms are those of a rapidly developing fever, which 

 becomes intense within a very short period. The animal becomes 

 dejected and inattentive to surrounding objects ; stands with its head 

 down, and not back on the halter as in serious lung diseases. In 

 the flanks, the muscles of the croup and of the shoulders, or of 

 the entire body it -has chills lasting from 15 to 30 minutes, and 

 frequently a grinding of the teeth which warns one that a severe 

 attack may be expected. The hairs become dry and rough and stand 

 on end. The body temperature increases to 104°, 104.5°, and 105° F., 

 or even in severe cases to 107° F., within the first twelve or eighteen 

 hours. The horse becomes stupid, stands immobile with its head 

 hanging, the ears listless, and it pays but little attention to the sur- 

 rounding attendants or the crack of a whip. The stupor becomes 

 rapidly more marked, the eyes become puffy and swollen with ex- 

 cessive lacrimation, so that the tears run from the internal canthus 

 of the eye over the cheeks and may blister the skin, in their course. 

 The respiration becomes accelerated to 25 or 30 in a minute, and the 

 pulse is quickened to 70, 80, or even 100^ moderate in volume and in 

 force. There is great depression of muscular force ; the animal stands 

 limp, as if excessively fatigued. There is diminution, or in some 

 cases total loss, of sensibility of the skin, so that it may be pricked 

 or handled without attracting the attention of the animal. On move- 

 ment, the horse staggers and shows a want of coordination of all the 

 muscles of its limbs. The senses of hearing, sight, and taste are 



36444°— 16 33 



