VALVULAR INSUFFICIENCY AND STENOSIS 79 



manifested by ascites, dropsical effusions, etc., in different 

 parts of the body. 



(6) Stenosis or contraction of the openings. In this con- 

 dition the opening is narrowed so that the chambers of the 

 heart are improperly filled. At the period of diastole, the 

 blood is held back at the entrance of the affected chamber, 

 and therefore normal filling of the chamber is interfered 

 with. This condition may occur at any of the openings of 

 the heart and will always induce imperfect heart action. 

 Every interference with an arterial opening causes imperfect 

 ventricular contraction; likewise defective venous openings 

 lessen the auricular contraction and power. This abnor- 

 mality in the action of the heart produces more or less 

 general disturbance in the circulation of the blood, and as 

 a consequence the reserve force of the heart is called into 

 action until compensatory hypertrophy can take place to 

 keep the circulation as near normal as possible. As soon as 

 the reserve energy is used, or the compensatory hypertrophy 

 fails to keep up the circulation, serious general symptoms 

 of defective circulation appear as is often observed in old dogs. 



Etiology. Valvular defects are produced by a variety of 

 causes : 



(a) Endocarditis is the most common cause (see Etiology 

 of Endocarditis). Endocarditis produces an inflammatory 

 thickening of the margins of the valves leading to their 

 imperfect closure. If the chronic inflammations persist it 

 leads to cicatricial contractions (stenoses), and often there 

 are found in long standing cases in old animals, deposits of 

 calcareous matter on the valves and around the openings. 



(6) Dilatation of the heart or weakness of the heart muscle 

 will sometimes affect the openings, the dilatation preventing 

 contact of the valve margins and a complete closure. 



(c) Certain poisons and toxins are causes \vhich lead to 

 alterations in the structure and ultimately the action of the 

 valves. 



(d) Atheromatous processes may produce the condition. 

 However this is not common in small animals. 



(e) Occurs during the course of some diseases, such as 

 anemia, pernicious anemia, etc. 



