Osteoma. ■ 353 



humor of both eyes in a cong-enitally blind colt (Renner), and 

 a chondroma the size of a fist in the wall of a calf's stomach 

 (first stomach). 



A chondroma should be looked ujjon as a dan.ijerons growth, 

 at times because of the position it may occupy, but also because 

 of its usual!}- marked tendency to grow large, and further because 

 it can give rise to metastasis. The cartilaginous masses hap- 

 pening to penetrate by growth into the veins sometimes develop 

 long processes within the lumen of the vessels, which are of 

 course obstructed; and any little portions which luay be carried 

 awav bv the blood may form metastatic nodes in other organs. 



In man there are seen from time to time pea-sized growths of cartilag- 

 inous tissue, peculiar in the marked vacuolation of their cells and in their 

 gelatinous consistence, at the base of the skull in the neighborhood of the 

 spheno-occipital suture; these, because of the bladder-like, swollen character 

 of the cells, were formerly known as cccliondromafa physaliformia, but are 

 recognized to be remnants of the notochord and are called chordomata. 



Osteomata. 



Bv the term osteoma or bone tumor is meant a definite new 

 formation presenting the structure of bone tissue and its mar- 

 row. According to the density of the calcified bone substance 

 there are distinguished (i) the cbiiniatcd osteoma (osteo))ia 

 chur Ileum ) which is of ivory-like hardness like the dense cortical 

 bone; (2) the spongy osteoma (osteoma spongiosum), of a more 

 cancellous t}pe, containing considerable marrow substance ; and 

 (3) the meduUar\ osteoma (osteoma medullosum) composed 

 principallv of marrow. In most instances the structure of the 

 bone (calcified matrix in lamellar arrangement about Haversian 

 canals, bone corpuscles in lacunre. bloodvessels, marrow cells 

 and fat) is characteristic; but. often as far as the marrow is 

 concerned, abnormalities are common, the medullary spaces being 

 occupied perhaps rather by spindle cells and fibrous connective 

 tissue (osteofibroma) or showing ^-^pecial abundance of round cells 

 and giant cells (osteosarcoma). Where the bone trabecula have 

 no lamellated structure and the bone corpuscles do not show 

 the usual projecting branches the specimen is spoken of as an 

 osteoid sarcoma. 



In manv cases it is dif^cult and even impossible to determine 

 whether a tumor-like osseous groAvth is really of autoblasto- 

 matous origin or is the product of inflaiumatory proliferation, 

 because definite lines of separation between the two cannot be 



