30 BOVINE PATHOLOGY. 



Caries especially affects articular surfaces of bones as well 

 as those portions invested by fibro- cartilage. In it no 

 tendency to repair is exhibited but the process of exten- 

 sion of the disorder progresses slowly, and removal of the 

 articular lamina of the bone by molecular disintegration 

 leads to death of the cartilage which it supports, and so 

 to roughness of a surface which for due performance of its 

 functions ought to be smooth. Hence results secondary 

 disease of the opposing surface, whether articular or ten- 

 dinous. The process of caries is remarkable for the small 

 amount of liquid product, and hence generally the absence 

 of marked distension of the joint capsule or wall of the 

 tendinous sheath. Ulceration is of much more general 

 occurrence, and as removal of tissue occurs at one part, 

 repair takes place at another. Pus is produced often in 

 very considerable quantity by ulcers, and may be of any 

 of the different kinds mentioned above. Ulcers are local 

 deficiencies of structure, which generally appear on mucous 

 membranes or the skin as breaches of the epithelial layer, 

 with the deeper layers of the membrane more or less in- 

 volved. In the cornea we sometimes see ulcers consisting 

 in local deficiency of the tissue of the cornea propria, in 

 which the conjunctiva is not involved ; this is due to the 

 fact that the latter membrane is supplied with nutriment 

 from a different source than the cornea. As a rule, the 

 epithelium is nourished by the deep-seated structures, and 

 is early involved in the diseased process. We must not in 

 all cases consider ulceration due to death of tissue-elements ; 

 it probably much more frequently results from cell pro- 

 liferation, which, replacing the parent by numerous cor- 

 puscles in a fluid medium, leads to breach of tissue, and 

 formation of a fluid with suspended cells, which either 

 escapes as pus, or is removed by the action of absorbent 

 vessels. The breaches of tissue resulting from ulceration 

 and suppuration are repaired by Granulation. This con- 

 sists in the production of small pointed projections over 

 the exposed surface, which are found to be composed of 

 cells, the deeper seated of which undergo organisation, 

 while the superficial degenerate into pus. By their 



