OSTEO-POROSIS. 189 



some of tliem, the whole of the interior was of a dark red colour, 

 from congestion of the vessels and effusion of blood into the 

 areolar interspaces ; in others, one-half only of the interior was 

 in this state, the other part being filled with a peculiar fat, and 

 consequently very pale in colour. It was at the end of the bone 

 affected in this way that the articular cartilage was of a palish 

 yellow colour, velvety to the feel, and also slightly greasy. Even 

 the teeth did not escape the malady, one of their constituents 

 being evidently affected, which was evinced by the crusta petrosa 

 being much thicker and more spongy than natural." 



The pathological anatomy of the bones was investigated by 

 Dr. G. Harley, and communicated to Professor Varnell in a 

 letter, dated 21st March I860:— "The horse's bones which 

 I examined for you presented two well-marked varieties of 

 morbid change, one of which was most characteristically seen 

 in the bones of the head, the other in the long bones of the 

 extremities. 



" 1st. As regards those of the head. The disease, although 

 it affected all the bones, was most advanced in the lower jaw. 

 I shall therefore limit my remarks to a description of it. The 

 bone was considerably hypertrophied in its tranverse diameter ; 

 the periosteum readily detached; the osseous tissue was of a 

 pink colour, and on pressure a quantity of blood oozed from its 

 surface, as if from a sponge. The osseous tissue was elastic to 

 the touch, and so soft that it could with facility be cut with a 

 knife. The surface of the section had a somewhat fleshy appear- 

 ance, but to the nail it conveyed rather the impression of carti- 

 lage. When examined microscopically the osseous tissue was 

 seen to be expanded into a network of fine fibres. The Haver- 

 sian canals, on the other hand, have become so enlarged that at 

 first sight they might be mistaken for bony tissue, and the bony 

 tissue mistaken for the Haversian canals. On examination with 

 a higher power, not only is the osseous tissue seen to be rarefied, 

 but the canaliculi proceeding from the lacunae or bone corpuscles, 

 i{s they were formerly called, are in many cases obliterated. The 

 lacunse themselves are also not so distinct as in healthy bone. 

 The enlarged Haversian spaces are filled with a gelatinous 

 matter, mingled with a small portion of fat, and here and there 

 pervaded with fine, scarcely visible fibres. 



" 2d. Long Bones of the Extremities. — The periosteum, although 



