198 
Diseases of Fish 
A superficial New Growth occurring in a Dog-Fish. 
Plate II. Fig. 2. 
Along the right side of a male specimen of Scyllium canicula 
there was a diffuse growth of greyish colour, stretching from about the 
level of the pelvic fins nearly to the tail. The growth consisted of 
multiple nodules which had coalesced over a great part of the affected 
area: in many places it had degenerated leaving the sub-dermal tissues 
exposed. The scales with their basal plates had disappeared in every 
part of the area affected by the growth. 
The right side of the fish was normal. 
The distribution of the growth roughly coincided with that of the 
mucous canals of the lateral line, but it had spread in all directions over 
an area not normally supplied with these canals. 
Sections (Fig. 2) showed a condition in many ways resembling an 
adeno-carcinoma. The growth consisted of irregular tubules containing 
masses of small cells. The walls of the tubules were composed of fibrous 
tissue, and the tubules themselves were nearly, or in some cases quite, 
filled with small oval cells. These cells possessed a relatively large 
amount of cell body and many of their nuclei showed various stages of 
mitosis. The cells near the walls of the tubules were more elongated in 
shape than those near the lumen of the tube. 
The dermal tissue underneath the affected area showed a certain 
amount of inflammation. 
Unfortunately only the posterior part of the body of the fish was 
available for examination: the head and viscera had been destroyed 
before the specimen came into my hands so it was not possible to 
determine whether secondary metastases had been formed. 
Dr Lazarus Barlow, of the Middlesex Hospital Cancer Research 
Laboratories, very kindly examined sections of the growth for me. He 
is of the opinion that though in many ways the tumour resembles an 
adeno-carcinoma, yet from a consideration of the histological details of 
the abnormal cells and their arrangement, it is probably of an endothe- 
liomatous nature and may be non-malignant. 
On a superficial examination of the sections the resemblance to an 
adeno-carcinona is very marked. The structure of the mucous canals 
of the lateral line appears to be reproduced with an abnormal proliferation 
of the columnar epithelial cells lining the glands. New mucous canals 
appear to have been formed and to ramify in all directions beyond the 
