CHAPTEK VI. 



TUMOURS. 



THE genesis, incidence, growth, and spread of tumours is much 

 influenced by anatomical considerations. 



Tumours may be classified into four groups : Tumours having 

 their origin in connective tissue, tumours having their origin 

 in epithelium, tumours designated dermoids, and tumours termed 

 cysts. 



CONNECTIVE-TISSUE TUMOURS. 



The fact that every tissue of which an organ is composed can 

 give rise to a tumour implies that a knowledge of the anatomy of 

 the organ, and therefore of its histology, is an excellent guide to 

 an enumeration of the primary tumours which may arise in it. 



A growing bone in a young subject affords a typical example. 

 Composing it will be found bone, both cancellous and com- 

 pact, cartilage, both articular and epiphyseal, periosteum, 

 red medullary marrow and fat. Thus an osteoma, chondroma, 

 sarcoma, myeloma, fibroma, or lipoma may be found in 

 connection with a growing bone. 



Osteomata, or bony tumours. 



There are two varieties of osteomata, the cancellous and the 

 compact. Speaking generally, developmental and anatomical 

 considerations account in great measure for the special position 

 and growth of the two forms. Cancellous osteomata are nearly 

 always associated with epiphyseal lines, and particularly with 

 that epiphysis from which the bone chiefly increases in length. 

 Thus the lower end of the femur, the upper end of the tibia, the 

 upper end of the humerus, and the lower end of the radius are 

 frequent sites of such bony growths. In their early stages they 



