Hypertrophy of the Heart. 429 



circle is soon completed, and the entire organ becomes diseased, 

 each constituent part of the organ operating injuriously on that 

 which preceded it in the track of the circulation, and every new 

 change forming but a stepping stone to a more dangerous modifi- 

 cation. 



On the other hand, the obstruction may exist in the general cir- 

 culation, on. the course of the aorta, or its branches, in its valves 

 at its origin from the heart, or in the narrowing of its orifice. 

 Then the increase takes place first in the left ventricle, is propa- 

 gated to the left auricle, leads to congestion of the veins, capil- 

 laries and arteries of the lungs, and lastly to disease of the right 

 side of the heart. Here there is a different starting point, but 

 the progress of the disease-changes, in a direction opposed to the 

 course of the circulation, is the same. 



The disease may, however, begin with the auricles, owing to 

 disease of the auriculo-ventricular valves impeding the flow of 

 blood into the ventricle, or to simple narrowing of the auriculo-ven- 

 tricular opening. The auricle is then primarily enlarged, the 

 corresponding veins congested, this is propagated to the capillaries 

 and arteries, and lastly the ventricle on the opposite side of the 

 heart is involved. This is chiefly seen with fibrinous deposits on 

 the valves or in the case of polypus hanging into the auriculo- 

 ventricular opening. Aneurisms, embolisms, neoplasms, atheroma 

 and calcic degeneration of the arterial walls may be effective 

 factors. 



In addition to these causes, Bouilaud andlycblanc attach a high 

 importance to chronic inflammations of the serous membranes, 

 which, by reason of the contiguity of the latter to the muscular 

 structure, bring about a more abundant circulation in this and an 

 increased nutrition. Another cause is unintermitting hard work 

 which necessitates excessive exertion of the heart, to supply 

 blood more freely to the muscular system and the lungs. Many 

 hunters suffer from this affection it is believed because of their 

 extraordinary exertions. The stallion Helenus had a heart of 

 14 lbs. 



Weight of the heart. The heart in the horse which rarely 

 weighs over 9 lbs. is increased from 10 lbs. to 14 lbs. in this dis- 

 ease and in one case in a cart horse, recorded by Stephenson in 

 the Veterinarian for 1861, it is said to have reached 32 lbs. 



