DEGENERATIVE NEW FORMATIONS. 95 



These are essentially different processes, and inay be 

 styled simple and numerical hypertrophy. 



Hyperplastic processes (numerical hypertrophy) in all 

 cases produce a tissue similar to that of the original 

 part ; hyperplasia of the liver gives rise to new hepatic 

 cells ; that of a nerve to new nerve-substance ; that of 

 the skin to a fresh production of the elements of the 

 skin. A heteroplastic process, on the contrary, engen- 

 ders histological elements which correspond, indeed, to 

 natural forms, elements, for example, resembling in 

 structure those peculiar to glands, nerve-substance, the 

 connective and epithelial tissues, but these elements do 

 not arise in consequence of a simple increase in the 

 number of such as previously existed, but in conse- 

 quence of a change in the original type of the parent 

 tissue. When cerebral matter forms in the ovary, it 

 does not arise out of pre-existing cerebral matter, nor 

 through any act of simple cell-proliferation ; when epi- 

 dermis springs up in the muscular substance of the 

 heart, however much it may correspond to that on the 

 external surface of the skin, it is, notwithstanding, a 

 heteroplastic structure. When we find hairs quite natu- 

 ral in structure in the substance of the brain, however 

 great the correspondence they exhibit with the hairs of 

 the external surface, they will nevertheless be hetero- 

 plastic hairs. In like manner we see cartilaginous tis- 

 sue arise, without the existence of any essential differ- 

 ence between it and ordinary, familiar cartilage, as, for 

 example, an enchondromata. Still, an enchondroma is 

 a heteroplastic tumour, even when occurring in bone, 

 for perfect bone has no longer any cartilage in the parts 

 where the enchondroma forms, and the term cartilage of 

 bone (Knochenknorpel), as a designation for the organic 

 basis of bone, is nothing but a term. It is either from 

 osseous or medullary tissue that the enchondroma 



