Melanoma. t,J7 



of which is best regarded as merely a lymphatic hyperplasia occas- 

 sioned by microorganisms or toxic substances which are in some 

 way brought to the lymph nodes (and some of these are tuberculous, 

 the remainder probably being products of a variety of microbic and 

 toxic influences). The second group may be properly referred to 

 the class of the sarcomas and spoken of as lymphosarcoma and 

 lymphadenoid sarcoma. The term lymphoma may be provisionally 

 retained to cover the group of uncertain or indistinguishable exam- 

 ples, but has no other place properly in tumor nomenclature. If 

 we limit ourselves to that series of cases, to which, from their 

 higher infiltrative and metastatic tendency (especially where we can 

 recognize that the secondary nodules are true metastases and not 

 mere hyperplasias of previously existing lymphoid foci which may 

 have been induced by an original microbic or toxic cause), the 

 name sarcoma may be reasonably applied. It should be added that 

 lymphosarcoma is a highly malignant type of sarcoma, ranking with 

 the ordinary small round cell variety in the severity of malignancy 

 from metastasis. It is. of course, difficult to make the separa- 

 tion in a large group of cases, but as far as possible we should 

 endeavor to exclude from the term lymphosarcoma tliose cases in 

 which enlargements manifest any appearances of infectious origin. 

 Where among these there is evidence of tuberculosis of course 

 the case is promptly referred to as tuberculous lymphatic hyper- 

 plasia. For the rest of the cases the non-distinctive term Hodg- 

 kin's disease may be employed if desired ; and it is well to keep 

 clearl}' in mind that the affection known as lymphatic leub^emia, 

 both acute and chronic, bears close relationship with the latter 

 group.] 



Melanomata. 



A mclaiionia. iiiclaiiosarcoiua (cliroiiiatoplwroma), or pig- 

 mented tumor, is characterized by a black-brown or slate-gray 

 color produced by the pigment cells (chromatophores) which 

 constitute the growth. Normally pigment cells are found as 

 specially difterentiated connective tissue elements in the skin 

 and choroid coat of the e_\e, and in some animals, as sheep, also in 

 the 'pia mater of the brain. The melanomata take their origin 

 from these cells and are therefore found most frequently in the 

 skin, being especially common in horses. It is peculiar that gray 

 and light colored horses, which as foals had a dark coat of hair, 

 should be especially prone to these tumors ; and it may be 



