AFFECTIONS OF THE VALVES AND ORIFICES OF THE HEAET. 577 



fibrinogenoiis or plastic and lymplioicl materials, which in 

 certain states of the blood are specially abundant. 



As a general rule none of these different varieties of abnormal 

 growths may, with any degree of certainty, be diagnosed 

 during life ; many animals may be sufferers from such and 

 give no indications of illness, while, where symptoms of cardiac 

 disturbance have been observed, these have as often been re- 

 ferred to other and very different states. Their existence has 

 only been discovered after death, which, in all probability 

 being sudden, called for an examination. As we are unable 

 to diagnose the existence of these abnormalities, and as they 

 so often, even when existing, seem to cause no inconvenience, 

 it were needless to speculate as to treatment. 



YI. Affections of the Valves and Orifices of the 

 Heart. 



The natural as well as unnatural cardiac sounds have already 

 been alluded to, and to a certain extent described (Chap. XXV.). 

 What are now to be taken up very shortly are certain definite 

 organic lesions productive of the 'murmurs' or abnormal 

 sounds associated with obstruction or regurgitation of the 

 blood in its passage through the orifices of the heart. 



Causes and Results of Valvular Disease. — The greater number 

 of the diseased conditions which are observed as connected 

 with the lining membrane of the heart and of the valves are 

 probably the direct result of inflammatory action, common or 

 specific. These are usually augmentation in bulk of the 

 minute textural elements entering into the composition of the 

 valves, or depositions on the surface of the membrane, in this 

 way causing thickening and puckering of these structures, 

 while the depositions, once established, possess a disposition 

 rather to increase than diminish. Or the valve-structures may 

 become the seat of warty excrescences of an atheromatous or 

 calcareous character. 



The common results of any or all of these changes upon the 

 valves are — 1. To thicken, corrugate, and render more bulky 

 the otherwise fine web-like structure, and thus obstruct the 

 flow of blood — valvular obstruction; 2. By the thickening 

 and puckering to contract the valve upon its base, and leave 

 the orifice insufficiently guarded — valvular insufficiency. 



37 



