474 bisejises of the cibculatoby system. 



affections are counterbalanced at the start by an increase of the 

 activity of the heart (compensatory hypertrophy). A compensatory 

 cardiac alteration in this way may not produce any serious symp- 

 toms for years; but, after violent exertions or excitements, we 

 observe more or less marked abnormal symptoms. Sooner or later 

 the cardiac muscle becomes tired and is no longer able to respond 

 to the task which has been created by the morbid condition. Cir- 

 culatory troubles then appear in the lungs and the system of the 

 vena cava. It is often at that period only that the animals are 

 known to be sick and we are called to treat them ; in most cases we 

 find an ensemble of symptoms hardly differing from that of advanced 

 cardiac hypertrophy. 



[The first symptom of chronic endocarditis which attracts atten- 

 tion is the marked weakness of the animals while at work. They 

 act somewhat like a dummy; they will stop, refusing to advance, 

 and do not respond to the voice or the whip; this, however, is of 

 but short duration. — w. L. z.] 



The principal manifestations of serious valvular lesions are : 



1. The acceleration of the pulse and of the heart rhythm, the 

 abnormal excitability of the latter, the irregularity of its contrac- 

 tions and of the pulse ; palpitations ; in exceptional cases, as in 

 contraction of the aorta in man, a slowing of the pulse is observed. 



[The intermissions constitute an entirely special form of rhythmic 

 disorder of the heart, and are not related to any substantial altera- 

 tion of this orgauo Quite common in the horse, they consist in a 

 short suspension of the heart's action, which are generally repeated 

 at every fourth, fifth, or sixth beating. With the exception of the 

 first contraction of each series, which is sometimes rebounding^ and 

 the usual very short interval which separates it from the second, the 

 others are normal as to force and rhythm. In some cases these 

 intermissions seem to correspond with a general disturbance of the 

 health, but, like the alterations, they may be seen in animals which 

 are in good condition and are used for hard work without showing 

 any symptom of indisposition. — w. L. z.] 



2. The difficulty of breathing, especially during exercise. In the 

 horse we observe true dyspuoeic attacks, designated as " cardiac 

 heaves.'' This dyspnœa, which generally dominates the scene, is 

 explained by the slowing of the pulmonary circulation and the per- 

 sistent connective tissue alterations (brown induration of the lung, 

 contraction of the pulmonary alveoli after capillary stasis). 



