328 DISEASES OF THE CIRCULATORY SYSTEM. 



Chronic arteritis, atheroma, or arterio-sclerosis, however, is 

 of frequent occurrence. The aorta alone may be affected, but 

 more commonly the whole arterial system is more or less uni- 

 formly involved ; the veins even may be involved ("angio- 

 sclerosis "). It is usually associated with sclerotic changes in 

 the heart and internal organs, and seems to be dependent upon 

 the same causes syphilis, gout, rheumatism, lead-poisoning, 

 chronic alcoholism, Bright's disease, and old age. It some- 

 times follows acute infections, as typhoid and scarlet fever, 

 and occasionally seems to be dependent on the cachexia of 

 cancer and tuberculosis. 



In the aorta at an early stage of the process there are pale 

 pinkish, rounded, or oval patches or nodules beneath the 

 smooth and unaltered intima, varying in size from a mere 

 point to half an inch in diameter. On cutting into one of 

 these patches it is found to be firm and fibrous ; in the centre 

 there may be a yellow focus of fatty degeneration. Micro- 

 scopically the patch is composed of dense fibrous tissue which 

 seems to have been produced by a proliferation of the subendo- 

 thelial connective-tissue cells ; at first many round, oval, and 

 stellate cells can be readily seen, but later the structure of the 

 affected area may be quite indefinite from advancing fatty 

 degeneration. The calcareous plates often met with in the 

 aorta are the result of the infiltration of such patches with 

 the salts of lime ; these plates may be so numerous as to alter 

 completely the appearance of the vessel. 



In the smaller vessels the changes are somewhat different. 

 Similar patches of opaque and firm tissue, one-sixth to one- 

 third of an inch in length, may occur at irregular intervals 

 along the course of the vessels. On cross-section of the artery 

 its lumen is seen to be considerably encroached upon at one side. 



In other cases endarteritis obliterans these patches are en- 

 tirely absent ; the lumen of the vessel is uniformly encroached 

 upon, sometimes almost obliterated by the increased thickness 

 of the intima produced by an active proliferation of the endo- 

 thelial and subendothelial connective-tissue cells. The muscle- 

 fibres of the media are atrophied, and there is usually a marked 

 thickening of the adventitia, the result of a round-celled in- 

 filtration which becomes more or less fully developed into 

 fibrous tissue. 



