242 INTERNAL SECRETION 



of serous infiltration of the media; proliferation of and hyper- 

 trophic changes in the muscles of the vessels, and injury of the 

 elastic elements in the vessel walls, especially of the lamina 

 elastica interna, together with consecutive, and probably com- 

 pensatory, proliferation of this tissue. In its earlier stages, it is 

 difficult to define the exact nature of the injury to the muscular 

 portion of the vessel walls. It is certain, however, that at a very 

 early stage there are softening of the tissue, nuclear changes, and 

 thickening of the fibres, the latter being probably compensatory. 

 In the case of vessels of the muscular type, the changes in the 

 intima the " hyperplastic proliferation of the intima ' are, as 

 a rule, apparent when the media are only slightly affected. At a 

 later stage, the proliferation of the intima in vessels of both kinds 

 becomes degenerative. 



The final stage consists in necrosis of the muscle cells (Erb, 

 Torri, Fischer, Hedinger, Lissauer, Kiilbs, Ziegler, Saltykow, 

 &c.), together with calcification of circumscribed areas, and 

 various changes in the elastic fibres. The question as to whether 

 the muscular changes are preceded by fatty degeneration has been 

 differently solved by different authors. Klotz, Saltykow, Pearce 

 and Stanton, Lissauer and Bennecke believe that this is the case; 

 on the other hand, Fischer, d'Amato and Flagella, and Scheide- 

 mandel have never observed fat. 



Where there are foci of calcification, the elastic lamella? fre- 

 quently appear to be stretched; their normal undulations dis- 

 appear; and "granulated, elastic' fibres are observed. Later 

 on, where the lesion is very pronounced, the elastic lamella? may 

 tear, or rather break, afterwards splitting and crumbling until 

 they finally disappear. Fatty degeneration of the elastic fibres 

 has also been described (Klotz). 



Calcification is frequently present at a very early stage. 

 According to Trachtenberg and Miesowicz, formation of cartilage 

 also takes place. At the beginning, the calcified foci are, as a 

 rule, sharply defined from the sound tissue. Where the media 

 is completely destroyed, a deep and progressive pouching of the 

 wall gradually takes place and an aneurysm is formed. The foci 

 and the chalky scales upon the media become surrounded later 

 by cellular proliferations, which consist of leucocytose and lym- 

 phocytose infiltration, granulation tissue and proliferation of 

 muscle cells. It is my own experience (Biedl and Braun) that 

 all these changes take place. The descriptions which have been 

 given of giant cells are doubtless well founded. The hyper- 

 trophic muscle fibres, especially in section, closely resemble 

 cartilage cells. In the later stages, there is connective tissue 

 formation (Ziegler), diffuse sclerosis, fibrous degeneration of the 

 media (Scheidemandel, Torri), reactive inflammation, mesarter- 

 itis, and endarteritis (B. Fischer). 



The changes in the intima consist, at first, of endothelial pro- 



