CHONDEOMATA. 67 



are capped by cartilage, and continue to increase in size so long 

 as there is cartilage left to ossify. They are not uncommonly 

 multiple. They are painless as a rule, but if they increase in 

 size to such an extent as to lie close under the skin of a part sub- 

 jected to pressure, an over-lying bursa may form, and inflamma- 

 tion and pain result. This may be typically present over an 

 osteoma at the lower end of the tibia, projecting so as to cause 

 friction of the skin against the boot. Again, local or referred 

 pain may be in evidence when an osteoma presses upon a nerve. 

 Barely actual paralysis may result from such pressure as when 

 an osteoma of the lower end of the femur implicates one or 

 other of the popliteal nerves. 



Compact or ivory osteomata are nearly always found upon 

 bones which have been developed in membrane. Hence they 

 are generally associated with the flat bones of the skull, and 

 with the mandible. They occur at times in the osseous wall of 

 the external auditory meatus, and from their position may lead 

 to annoying deafness by filling up the canal. The air spaces of 

 the frontal bone form another site for their incidence, as also 

 does the angle of the mandible. 



Exostoses, or bony out-growths, occur chiefly at the attach- 

 ments of certain muscles, as, for instance, the lowest part of the 

 insertion of the adductor magnus, causing an elongated adductor 

 tubercle. Also they are met with frequently on the terminal or 

 ungual phalanx of the great toe, probably induced by the inter- 

 mittent pressure to which this part is so subject. 



Chondromata, or cartilaginous tumours. 



Tumours composed of cartilage generally arise from the 

 cartilage in connection with growing bones, but they are also 

 formed in organs which at one period of development contained 

 cartilage. 



Associated with bones they will naturally be seen as out- 

 growths from epiphyseal cartilages, or more rarely as endosteal 

 tumours derived from islets of diaphyseal cartilage left behind 

 unossified. In the latter case they are usually found expanding 

 metacarpals or phalanges, and are in most instances multiple. 



52 



