THE CIRCULATORY SYSTEM. 461 



3. VARICOSE DILATATION. Portions of the wall of the vein undergo 

 saccnlar dilatation. The wall of the sac is formed of the coats of the 

 vein, but these may be thickened or thinned; the middle coat may dis- 

 appear entirely. There may be only one such dilatation, or there may 

 be a number on the same vein, or a number of veins may be affected at 

 the same time. The vein may be otherwise normal, or, more frequently, 

 is more or less uniformly dilated. 



4. ANASTOMOSING DILATATION. A number of contiguous and 

 anastomosing veins are dilated, both in the cirsoid and varicose forms. 

 The vein then looks like a series of cavities separated by thin partitions. 

 The dilatations of the same vein become adherent to each other and to 

 those of the adjoining veins; portions of the walls of the dilated parts 

 may atrophy so that there may be a number of cavities containing venous 

 blood and separated from each other by thin partitions. 



DISTRIBUTION, CAUSES, AND EFFECTS OF PHLEBECT ASIA. Sponta- 

 neous restitution of dilatations of the veins is not common, and usually 

 occurs only in the lesser degrees of the lesion. The tendency of the dila- 

 tation is to increase. Thrombi frequently form in the dilated veins, and 

 either partially or completely fill them. These thrombi may become 

 organized, or they may dry and become calcified, forming phlebolitlis, and 

 by the formation of new connective tissue in the walls they may become 

 enclosed in a fibrous capsule, with the obliteration of the vessel. The 

 wall of the dilated sac may become so thin -that it finally ruptures. 

 Inflammation of the dilated vein may occur, followed by fibrous thick- 

 ening. 



When occurring in mucous membrane, dilated veins are usually asso- 

 ciated with persistent catarrh. There is hardly one of all the veins of 

 the body which may not be dilated. The hsemorrhoidal veins forming 

 "haemorrhoids"; the veins of the leg and thigh; those of the pelvis and 

 pelvic viscera; those of the spermatic cord, scrotum, and labia; those of 

 the abdominal wall ; those of the neck and arms are most frequently 

 involved. 



The immediate cause of dilatation is usually some obstruction to the 

 passage of the blood through the veins toward the heart ; but alterations 

 in the walls of the vessels from degeneration, inflammation, or injury 

 are often important predisposing factors. 



WOUNDS RUPTURE. 



Wounds of the veins usually heal by a simple contraction and an 

 adhesive inflammation of their walls ; sometimes by the formation of a 

 thrombus. Rupture of the veins may be produced by severe contusions 

 and crushings of the body and by violent falls. Perforation of a vein 

 may be produced by suppuration of the soft parts and the invasion of 

 the walls of the vessel ; by the pressure of an aneurism or of a new 

 growth ; by the thinning of the wall of the vein in phlebectasia. 



