THE CIRCULATORY SYSTEM. 425 



part (Fig. 222). This may give rise to no symptoms, unless disease of the heart or 

 lungs be superadded. 



V. Either of the auriculo-ventricular orifices may be entirely closed. The fora- 

 men ovale remains open, and the ventricular septum is defective. ' 



VI. The valves of the different orifices of the heart may be absent or defective. 

 The arteries or the ventricles are usually defective at the same time. 



The aortic and pulmonary valves may consist of two large or four small leaves, 



FIG. 223. FENESTRATION OF THE SEMILPNAR VALVES. 



instead of the usual three. The edges of the semilunar valves maybe fenestrated (Fig. 

 223). These alterations are usually of no significance. 



Generally speaking, the existence of openings between the two auricles or the two 

 ventricles, admitting some admixture of venous and arterial blood, produces no marked 

 change in the circulation. If, however, the passage of the current of venous blood into 

 the right heart is in any way interfered with, the consequences are very serious. Cya- 

 nosis is produced, the skin is of a bluish color, the small veins and capillaries are dilated, 

 exudation of serum and hypertrophy of connective tissue take place, especially in the 

 fingers and toes. 



There may be absence of the heart; abnormal septa and chordae tendinese (Fig. 

 224) in the heart cavities; abnormal shapes of the heart. Very rarely two more or less 

 perfect hearts are found in the same thorax. 



MALPOSITIONS OF THE HEART. (1) There is a smaller or larger defect in the walls 

 of the thorax, so that the heart projects on the outside of the chest; the pericardium is 

 usually absent. 



(2) The diaphragm is absent, and the heart is in the abdominal cavity. 



(3) The heart is in some part of the neck or head ; this occurs only in fretuses very 

 much malformed. 



(4) The heart is transposed, being on the right side. 



ABNORMAL SIZE OF THE HEART. (1) The heart may be abnormally large in con- 

 nection with obstructive anomalies of the great vessels. 



(2) The heart may be abnormally small (hypoplasia). This abnormality is apt to 

 be associated with the so-called status lymphaticus (see page 367). 



DISPLACEMENTS OF THE HEART. Changes in the position of the heart are con- 

 genital or acquired. The congenital malpositions have already been mentioned. 



The acquired malpositions may be associated with : 



1. Hypertrophy of the heart; its long axis approaching the horizontal position. 



2. Changes in the thoracic viscera. Emphysema of both lungs may push the heart 



1 Consult for a study of rare forms of cardiac anomalies, Ilektoen, Am. Jour. Med. 

 Sciences, vol. cxxi., p. 163, 1901, bibl. 



