Fig. 139
Anastomosing circulation in sartorius and pectineus of dog, three months after ligature of femoral. (After Porta.)
Collateral venous circulation, from a woman aged forty-seven, under the care of W. W. Gull, in whom the inferior vena cava was completely obstructed from cancer. (Guy’s Hosp. Mus., Drawing 44⁴⁰.)
Direct anastomosing vessels of right carotid of goat, five months after ligature. (After Porta.)
The readiness with which vessels, both arteries and veins, lend themselves to the exigencies of extra work has long been recognized, and the natural provision for collateral circulation is one of which surgeons have for centuries availed themselves. On the contrary, vessels which are no longer needed or whose function is lost will undergo atrophy almost to obliteration; thus after amputation of the thigh the corresponding iliac vessels become much reduced in size ([Figs. 137], [138] and [139]).
ARTERITIS; ENDARTERITIS.
That arterial walls are resistant is shown by the fact that they are usually the last tissues to yield to gangrene. Whether a primary acute arteritis often occurs is a question of less interest in this place than the fact that even arterial walls will succumb to infection and that secondary hemorrhages from ulcerative processes are by no means rare. The pathological processes which occur in the various structures of the heart are repeated in the arterial walls; thus there may be a periarteritis corresponding to pericarditis, a mesarteritis which in many ways resembles myocarditis, and an endarteritis which corresponds more or less closely to endocarditis, and all of these in their acute or chronic forms. The acute forms which concern the surgeon are due usually to the presence of infected emboli, which have the same effect upon the arterial walls that infected thrombi have upon the venous walls, i. e., they lead to occlusion, infiltration, and suppuration.
Of the more chronic types those produced by syphilis are the most common. Here it is usually the outer and inner coats which suffer most. Tuberculous infection of an artery is of frequent occurrence and pertains only to those vessels which are in intimate relation with previous tuberculous lesions, while the syphilitic forms are diffuse and generalized and as likely to involve one part of the body as another. It is well known that arteritis in various degrees of intensity may be met with in most of the infectious diseases. Whether they are due to the living germs or to toxins generated during the process concerns us at this point but little. It is of importance, however, to realize that vessels so compromised may thus receive their first impetus to degeneration and subsequently form aneurysm. The degenerative types of greatest interest to the surgeon are fatty degeneration, which occurs in the interior rather than the exterior, and calcification, which is rather an involvement of peripheral vessels and which occurs mainly in the middle and the outer coats. The latter may be limited or may involve an entire vessel. When the radial arteries are involved the condition may be appreciated at the wrist. Calcification frequently follows other degenerations, especially fatty, of the intima, and then may be seen in the interior of an artery. A true ossification has been described, but is exceedingly rare.