260 CIRCULA^TOEy APPARATUS, 



gpongy. The pores correspond to the lumina, the septa to the 

 fused walls of those veins which have undergone dilatation and 

 varicose degeneration. We must suppose the structure in ques- 

 tion to be produced by atrophy of the interstitial connective 

 tissue ; this wastes under the pressure of the distended veins, 

 which is kept up by the persistently increased tension of the 

 blood in their interior ; so that, after a time, nothing is left save 

 only the walls of the veins themselves. Inflammatory action is 

 often set up about these venous plexuses ; it may either result 

 in induration or in suppuration. The blood may coagulate here 

 and there in their interior, causing partial gangrene. 



§ 231. Next to the veins of the pelvic viscera, plilebectasy 

 most frequently affects the branches of the great saphena. Any 

 circumstance which retards the flow of blood through the common 

 iliac vein — as e.g. the pressure of the gravid womb or of a pelvic 

 tumour — may give rise to this accident. It may also be caused 

 by prolonged contraction of the muscles of the leg, as e.g. in 

 persons who have to work standing ; the muscular contraction, 

 by compressing the deeper veins of the leg, drives the blood into 

 the subcutaneous channels. Then gravity helps. Generally 

 speaking, dilatation of the saphena is due to the co-operation of 

 several distinct factors. Its various stages may be followed even 

 through the overlying skin. In its milder as well as its more 

 severe forms, it often underlies those chronic inflammatory and 

 ulcerative disorders of the lower limbs, whose obstinacy so often 

 exposes the temper of both physician and patient to severe 

 trials. 



y^ Dilatation of Capillaries, — Telengiectasis, 



§ 232. Apart from the more or less transitory dilatation 

 consequent on hyperaemia, there is really no condition of the 

 capillary vessels which can be compared to aneurism or phlebec- 

 tasy. The disorder specifically termed ^'telengiectasis" consists 

 in an over-production of capillaries in circumscribed jDortions of 

 the skin. The parench3ana of many organs, among others that 

 of the skin and its proximate constituents, the papilla}, glands, 

 clusters of fat-cells, &c., is primarily divided into territories by 

 that system of anastomosing lacunar in the connective tissue, 

 whose nodal points contain the connective-tissue corpuscles. The 

 thick protoplasmic processes of these corpuscles map out the 



