254 CmCULATOEY APPARATUS. 



preceded them. They are at first sinuous ; i.e. a probe passes 

 tlirough a small hole into a cavitj which bmTows some way 

 underneath the surface. This cavity is that of the former abscess ; 

 it may be more or less distended with coagulated blood ; as a 

 rule it is empty. Moreover the thin membrane by which it is 

 still roofed in, has a tendency to roll up from the hole to the 

 margins of the cavity — the aperture increasing proportionately 

 in size ; more rarely, it is detached in shreds ; in any event, 

 the open atheromatous ulcer forms so marked an inequality of 

 the surface, that it may readily give rise to coagulation ; the 

 adherent thrombi may be of considerable length, hanging from 

 the wall of the vessel into its interior.* 



§ 219. The second mode of retrograde metamorphosis which 

 is met with in association with atheromatous degeneration, also 

 begins as a rule in the deeper parts of the indui'ated intima. It 

 consists essentially in an impregnation of the intercellular sub- 

 stance with earthy salts — a calcification. It gives rise to bone- 

 like plates of variable size and form, often so large that e.g. the 

 entire aortic arch is converted into a single bony tube. We not 

 unfrequently find a number of small bony lamellae, not exceed- 

 ing half-an-inch in any diameter, scattered through the intima ; 

 the finger at once detects their presence. When shelled out of 

 their capsules, most of them exhibit a saucer-like depression 

 which corresponds to the curvature of the vessel ; their edges 

 are sharp. These edges are the first to perforate the superjacent 

 layers of the intima, forming jagged projections and affording 

 fresh opportunities for the production of thrombi. The partial 

 detachment of larger bony lamellgs in consequence of fatty 

 degeneration of the surrounding parenchyma is not unusual; 

 complete separation however is rare. 



I have never been able to convince myself that true bone is 

 really formed, although this might fairly be inferred from the 

 process being usually designated '^ ossification." The lamellae of 

 the intima are simply calcified and may be restored to their 



* In the interior of an atheromatous deposit which was nearly quite 

 softened, I observed a small, button-like, soft mass, which contained 

 blood- vesselg and had evidently grown from the middle coat. On more 

 careful examination I discovered a whole series of such buttons under 

 the same indurated patch. They consisted, apart from the capillary 

 loops, of hyaline mucous tissue whose cells had undergone fatty de- 

 generation. (20th July, 1867.) 



