286 G. H. DREW. 



experience of the histology of inflammation and muscular degeneration 

 in fish, it might very easily be diagnosed as such. The sections showed 

 that there was a great increase in the number of the muscle nuclei, 

 and loss of definite striation of the fibres, followed by atrophy : some 

 increase in the amount of fibrous tissue surrounding the muscle 

 bundles had taken place, and in many cases this thickened muscle 

 sheath was filled only with muscle nuclei and leucocytes, all trace of 

 the muscle itself having disappeared. Fibroblasts in all stages of 

 division were present as well as many leucocytes. 



The blood capillaries in the neighbourhood were dilated, and in 

 regions where the inflammatory process was most severe, irregular 

 blood spaces without definite walls were found. The whole of the 

 diseased area was crowded with minute pigment granules, often 

 aggregated into small masses ; many of the leucocytes contained large 

 numbers of these pigment granules, but otherwise the granules were 

 always extra-cellular. The skin showed little sign of disease, but 

 contained a few pigment granules in the dermis, deposited in thin 

 layers parallel to the surface ; the most intense area of pigmentation 

 was between the dermis and the muscles, where an almost continuous 

 sheet of pigment had been formed. 



I have experimentally produced a condition closely resembling this 

 melanotic myositis by long-continued repetition of the application of a 

 strong solution of Iodine to a circumscribed area of the skin of 

 Eundulus heteroclitus. In cases where the irritation due to the 

 Iodine was sufficiently intense to cause inflammation of the subdermal 

 muscular tissue, a condition characterised by atrophy of the muscles, 

 great multiplication of the muscle nuclei, and development of pigment 

 granules, accompanied by the usual phenomena of inflammation, was 

 produced. In this case also the presence of numbers of cells arising 

 by multiplication of the muscle nuclei, together with the pigment 

 granules and leucocytes, gave at first sight a picture suggestive of a 

 sarcomatous growth of a melanotic type. 



The particular swelling here described as occurring in a mackerel 

 may thus be considered as a melanotic myositis of unknown cause, and 

 it is perhaps worthy of note that the formation of granules of a 

 pigment apparently resembling melanin can be artificially produced in 

 the tissues of fish by causing mild but continued inflammation. 



DESCRIPTION OF PLATE IV. 



Illustrating Mr. G. H. Drew's 'paper on " Some Cases of Neio Groivths in Fish." 

 Fig. 1 X |. Photograph of Fibro-sarcoma of Raia macrorhynchiis, cut open to show 

 internal surface and origin from perichondrium of one of the 

 fin rays. 



