296 



CirvCTJLATOEY APPAEATTJS. 



3. Congenital Malformations of the 

 CmcuLATORY Apparatus. 



§ 260. Among congenital malformations of the circulatory 

 apparatus, retarded development of the circulatory system as a 

 wholcj in comparison with the remaining parts of the organism, 

 deserves the first place. This shows itself primarily in an ab- 

 normal smallness of the heart ; the calibre of the aorta and its 

 jorincipal branches being proportionately narrowed and their 

 walls thin. Careful investigation proves that all the smaller 

 arteries and veins are more feebly constructed than they should 

 be. This condition, which principally affects persons of the 

 female sex, is nearly always complicated with corresponding 

 defects in the development of the blood (sa^ Chlorosis, § 176), and 

 of the sexual oro-ans : but which of these three sets of deficiencies 

 ought to be regarded as primary, and which as secondary, must 

 remain uncertain. The membranous part of the ventricular 

 septum is deserving of especial notice in these cases, inasmuch 

 as it is usually very large, and predisposed 

 to aneurismal dilatation (§ 251). 



§ 261. A second group of congenital 

 malformations depends on some disturb- 

 ance of the earliest stages in the develop- 

 ment of the heart and great vessels. 



Everybody knows that the heart origin- 

 ates as a straight contractile tube in the 

 middle line of the area germinativa. This 

 tube presents three dilatations (fig. 94), 

 the sinus venarum communis, the ventricle, 

 and the hulhus aorta'., besides a number of 

 vascular arches wliich spring in pairs 

 from the aortic bulb. The shading in the 

 annexed diagram serves to distinguish 

 those of the vascular arches which are 

 ultimately obliterated, from those which re- 

 main as permanent trunks ; the dotted line 

 indicates that a partition, growing from before backwards, separates 

 the innominate trunk from the left carotid and subclavian. The two 

 latter vessels are then displaced along the aortic arch until they 

 reach the points at which they are given off in the adult animal 



Difigraraniatic repre- 

 sentation of the de- 

 velopment of the heart 

 and great arterial 

 trunks. 



