474 Proceedings of the Royal Physical Society. 



are seen, in which still further changes are taking place. The 

 muscular coat is still fairly well defined, but in it are numer- 

 ous small round cells similar to those mentioned above, each 

 consisting of a nucleus and a very thin film of protoplasm. 



What corresponds to the inner coat is now seen to be 

 simply a vitreous or caseous mass, which is evidently com- 

 posed of the proliferated cells of flattened layers and of the 

 altered formed material which lies between the cells. The 

 lumen of the vessel is completely occluded ; blood could no 

 longer pass to supply the vessel walls and the tissues to 

 which they run. After a careful examination of these 

 obliterated vessels in both longitudinal and transverse 

 sections, one is forced to the conclusion, that what we have 

 described is taking place in a great number of the small 

 arteries. The whole of the obstruction is not necessarily 

 due to thickening of the inner coat, for in some of the 

 sections examined the remains of a small blood clot could 

 be seen filling up what remained patent of the lumen, 

 completing the occlusion. Here, then, we have a definite 

 course of events. Be the cause what it may — and the 

 evidence points strongly in the direction of Parasitism, 

 though as yet no actual micro-organism has been distin- 

 guished in this position — there is inflammation of the walls 

 of the vessel leading to infiltration of the T. adventitia with 

 small round cells, to less marked changes in the muscular 

 coat, and to extremely well-defined changes in the inner 

 coat, which becomes enormously thickened ; in consequence 

 of this thickening, the lumen of the vessel becomes very 

 much diminished, the wall is no longer smooth and regular, 

 and eventually a blood clot is formed in the nan owed tube, 

 which is thus effectually closed ; what follows, is what would 

 be expected under the circumstances. The walls of the 

 vessels are considerably altered, but although there is such 

 a great increase of cellular tissue, there is no corresponding 

 increase in the number of blood vessels or in the nutritive 

 supply to the walls of the vessel, consequently when the 

 clot is once formed it is practically cut off from all food 

 supply, and the altered T. intima is similarly situated. The 

 clot in the centre of the patch first undergoes caseation, or 



