Report on Diseases and Abnormalities in Fishes. 21 



M'Intosh describes a myxoma in the plaice. It had a general 

 resemblance to the tumour in the pectoral region of the saithe 

 described above. Its principal bulk lay on the left side of the fish, 

 but it had extended between the neural spines to the right side. 

 Many of the neural spines were distinctly curved. 



Angioma. 



Cod. — A large pendulous tumour was firmly attached to the rete 

 mirabile of the swim-bladder. It is shown in half-size in fig. 98. 

 It was roughly ovid in shape, and measured 95 cm. by 6 cm. The 

 inside layer of the wall of the swim-bladder was yellowish and soft. 

 The outside skin of the tumour was .somewhat hard, but it broke 

 up and came off in shreds. The tumour could be readily torn. 

 Fig. 97 represents a slice 25 cm. in thickness. The solid tissue is 

 spongy : there are several large cavities. 



The distal part contained coagulated blood : the proximal part is 

 full of normally-coloured blood. Fig. 94 represents some of the blood 

 corpuscles. It appears to be a blood-vessel tumour. 



A portion of an angioma from a cod was sectioned by Dr. F. 

 M. Milne. A small part of one of the sections is shown in fig. 54. 

 Gp., tumour on lemon sole, p. 22. 



Tumours in the Peritoneum. 



A Ling (Molua molva) which had been caught off the West Coast 

 of Scotland had a large number of tumours on the wall of the abdo- 

 men (fig. 51). In the figure the dotted regions represent the tumours. 

 The} r were thickly arranged along the swim-bladder. The tumour 

 was a thickening of the peritoneum. It was white, fibrous, almost 

 gristly in nature. 



The abdominal cavity has a three-layered lining (fig. 121). The 

 first is the peritoneum (per.), which is vascular. Next come two 

 colourless thin fibrous layers (1/., 2/.), which rest directly on the 

 muscles. The peritoneum is attached equally all over to the fibrous 

 layer. The two fibrous layers have strong attachments to the 

 aponeurosis between fhe muscle segments ; the lower layer is loosely 

 attached to the muscles. The arrangement of the two fibrous layers 

 is shown in fig. 123 ; the fibres run approximately at right-angles 

 to one another. 



The tumour is formed in the peritoneum (fig. 121), which has 

 become fibrous tissue at the place. In the centre it has a sort of 

 root (rt., fig. 124), which penetrates the fibrous layers, to be in one 

 case attached to the aponeurosis of the muscle. The separation of 

 the fibres of the lower lavers to permit of the passage of the root is 

 shown in fig. 125. 



The tumour can be lifted right off the fibrous layers by severing 

 the root, but one cannot separate the peritoneum from it without 

 tearing the tumour (figs. 121 and 124). Some of the silvery- white 

 pigment of the peritoneum can be seen on the under-surface of the 

 tumour. The two fibrous layers were thickened into a cushion 

 below this tumour. The root of the tumour may be the attach- 

 ment of vessels. Some of the tumours have a brown-coloured 

 central region, which can be dissected out as a separate solid. 

 Might it indicate an earlier growth of the tumour? The small 



