413 



8IMPLK TUMOURS. 



V. — CAHTILAGINOUS TUMOURS, OR ENCHONDROMATA. 



These may take place in the soft parts, or in bone; their 

 favourite seat being the region of the sternum, or upon the ribs. 

 They are frequently caused by external injury. There are two 

 forma of them ; one being round or oval, with •well-defined 

 borders, and the otlier having no well-defined limits, but resem- 

 bling an infiltration into the surrounding structures. In the 

 latter case it will geneially be found that the tumour arises from 

 the development and growth of carti- 

 lage in an inflammatory exudate; and 

 wounds involving the sternum are very 

 apt to be accompanied by this compli- 

 cation. 



To the touch these tumours ai'e hard 

 and dense, but present a slight elasticity. 

 They gradually increase in size, and 

 when on the sternum become a source 

 of hindrance to the animal's movements, 

 causing him to move with the fore legs 

 wide ajoart, and with apparent stiffness 

 in the gait. The skin over the en- Jiff- 82. -Proliferation of 



° diseased cartilage. Large 



largement soon becomes raw by the groups of cartilage cells within 



a common envelope (wrongly 

 called parent cells), produced 

 from single cells by successive 

 subdivisions. At the edge one 

 of thcRe groups has been cut 



as a globular enlargement, hard and through, and in it is seen a 

 firm to the touch, causing litUe or no r;itfoftp.l°X™ [»* 

 inconvenience to the animal, unless temai secreted masses). 300 

 interfered with by the collar. lam.— ir how.; 



I am not aware that these tumours grow within the shell .of 

 a bone, as in tlie human being, but on the outside, and gene- 

 rally fastened to the bony wall and invested by the periosteum, 

 which is greatly thickened and overgrown. When cut with the 

 knife, they present a bright, greyish, translucent, or pinky- white 

 appearance, and sometimes coarsely granular, or opaque, with 

 pntty points, as if gradually ossifying. When examined micro- 

 scopically, they are found to consist of cartilage cells, mixed with 

 fibres of white fibrous tissue. The fibres are very delicate and 

 tufted, and contain the cartilage cells, either singly or in groups. 



friction of the elbow on its surface. 



The rounded form of tumour gene- 

 rally appears on the cariniform caitilage 



