278 THE MICROSCOPIST. 



are sometimes nodular, like millet-seeds or grains of wheat, 

 isolated or in groups. 



g. Cartilage Type. 



1. Enchondroma or Cartilaginous Tumor. Like carti- 

 lage, this consists of cells and intercellular substance, the 

 latter being hyaline, fibrous, or mucoid. The cells are 

 often spindle-shaped or stellate. Enchondromata rarely 

 develop from cartilage, but from bone and connective tis- 

 sue. A large majority have their seat upon bones, espe- 

 cially at the diaphyses of the long bones. They are usu- 

 ally single, except on the fingers and toes, where they are 

 often multiple. An ossifying enchondronia is called osteo- 

 chondroma. The enchondromata, especially those which 

 originate from cartilage, may be regarded as benign, yet 

 encapsulated forms originating from bone or connective 

 tissue are often injurious from the rapidity of their growth. 

 The softer forms, such as occur in the medulla of bone, 

 are sometimes malignant. 



h. Type of Bone Formation. 



1. Osteoma. An osseous or bony tumor. An outgrowth 

 from pre-existing bone is an exostosis or osteophyte. Such 

 outgrowths proceed from the periosteum, the articular 

 cartilage, or the medulla. In the latter case they might 

 be properly termed enostoses. These are homologous tu- 

 mors, since they are similar in structure to the tissue in 

 which they are found. The osteomata, however, may be 

 heterologous, as growing from connective tissue or carti- 

 lage apart from bone. They are of two kinds : 1. The 

 ivory or hard tumors, in which there is a marked absence 

 of cancellated bony tissue. 2. The soft or cancellous, 

 which are spongy. The medullary cavities are sometimes 

 quite large. 



Osteomata are innocent tumors. Those osseous growths 



