The arterial system presents numerous varieties of irregular narrowness, and, moreover, exhibits many differences in respect to its extent and degree. To this class belong congenital anomalies.

1. A Congenital Abnormal Narrowness Of The Aortic System

A Congenital Abnormal Narrowness Of The Aortic System, which is strikingly apparent in the large arteries, and more especially in the trunk of the aorta. This is found in some cases, in adults, to be contracted, particularly in its descending arch, to the calibre of an iliac or even of a carotid artery. This anomalous condition, which is very generally associated with deficient development of the system, and with a striking thinness and softness of the arterial walls, is often overlooked in childhood, and very commonly does not exhibit any distinct symptoms until the period of puberty, when it manifests itself by insufficiency in the calibre of the artery compared to the quantity of the blood, and by dilatation of the heart, more especially of the left ventricle. It most frequently occurs in females, and is combined with retarded development generally, and more especially with smallness of the sexual organs.

Anomalies of various extent, amounting even to entire occlusion, are occasionally exhibited in the trunk and branches of the pulmonary artery, occurring as congenital conditions, combined with, and depending on obstructions in the interior of the heart.

2. A Congenital Deficient Development Of Separate Portions Of The Arterial System

A Congenital Deficient Development Of Separate Portions Of The Arterial System, more especially in relation to the calibre and elaboration of the coats of the vessels supplying undeveloped, stinted parts and organs of the body.

Acquired Abnormal Narrowness appears under many forms, and frequently attains so great a degree as to present complete occlusion of the artery. All the various contractions, and the atrophies in which they result, may be principally referred to a simple involution of the artery, to contraction and obliteration in consequence of disease of the coats of the vessel, to occlusion of the artery, and to contraction and obliteration depending on pressure on the artery.