490 TUMORS. 



formations 5 they occur at the articular ends, mostly, of the 

 humerus and the femur, analogous to the processus trochleares 

 of some animals. To these may be added the bony formations 

 at the points of insertion of the tendons, muscles, and aponeur- 

 oses, which Virchow termed exostoses apophyticce. They are 

 either directly connected with the bone, or take rise independ- 

 ently of it (so-called tendon bones). These bony structures orig- 

 inate, unconnected with inflammation, perhaps on account of an 

 excess of lime-salts in the organism. Maslowsky has succeeded 

 in producing calcareous deposition and ossification in the mus- 

 cles of animals, in the vascular system of which, for a certain 

 length of time, he had injected lactate of lime. Bony formations 

 in the dura mater, the muscles, and the lungs are products of 

 inflammation. 



(~b) Compact or eburneal osteoma is a rare tumor; it occurs on 

 the bones of the face, the skull, the scapula, the pelvis, and the 

 phalanges; its favorite locality is the frontal bone. It has a 

 smooth or slightly nodulated surface, and very rarely attains any 

 considerable size. It is composed of a more or less regularly 

 lamellated bone-tissue, imitating in its structure the outer per- 

 ipheral layer of compact bone, and is scantily supplied with 

 medullary spaces. These, on the surface of the tumor, are, as a 

 rule, large, and contain several blood-vessels; while the main 

 mass shows only irregular Haver sian canals, which contain one 

 capillary blood-vessel. Toward the point of attachment the com- 

 pact bone formation usually blends with the cancellous structure. 

 (See Fig. 189.) 



The cement-layer of the roots of teeth not infrequently 

 develops into compact osteoma, which sometimes reaches a 

 considerable bulk. Tumors of the dentine are entirely dif- 

 ferent formations ; for their designation Virchow has pro- 

 posed the term odontoma. These are composed of dentine, with 

 irregularly arranged dentinal canaliculi, similar to formations 

 of secondary dentine and the so-called pulp-stones. (See chapter 

 on teeth.) 



Bone-tissue is often found combined with other varieties of 

 tumors, such as fibroma, chondroma, myeloma, and it is asserted 

 that it also unites with cancer and forms the " malignant oste- 

 oid" of Joh. Miiller. The terms employed to designate tumors 

 of these varieties are osteo-fibroma, osteo-chondroma, and osteo- 

 myeloma. In all these instances the bone-tissue is unquestiona- 

 bly a secondary formation. 



