418 



SIMPLE TUMOUES. 



V. — CAKTILAGINOUS TUMOURS, OE ENCIIONDEOMATA. 



Tliese 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 

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

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

 bling an infiltration into the surrounding structures. In the 

 latter case it will generally 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 are 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 apart, and with apparent stiffness 

 in the gait. The skin over the en- 

 largement soon becomes raw by the 

 friction of the elbow on its surface. 



The rounded form of tumour gene- 



¥icr. 82. 



Proliferation of 

 diseased cartilage. Large 



groups of cartilage cells within 

 a common envelope (wrongly 

 called parent cells), produced 

 from single cells by successive 



,-ally appears on the eariniform carriage T^^o^X^^S Z 

 as a globular enlargement, hard and 

 firm to the touch 

 to 



through, and in it is seen a 

 cartilage cell invested by a 

 number of capsular layers (ex- 

 ternal secreted masses). 300 

 diam.— (ViKCHOW.) 



causing little or no 

 mconvenience to the animal, unless 

 interfered with by the collar, 



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

 a bone, as in the 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 

 api^earauce, and sometimes coarsely granular, or ojmque, with 

 gritty 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. 



