Report on Diseases and Abnormalities in Fishes. 15 



by 3{ inches ( 8 m.). It was bound to the aponeurosis by a fibrous 

 tissue. Its main bulk was on the left side, but it extended through 

 between the dorsal spines to the right side of the body. The 

 tumour had not replaced the muscles ; it had pushed them apart, or 

 possibly prevented their full growrh. When cut across, the tumour 

 was found to be white inside (fig. 152). In parts there was some 

 black pigment in irregular specks. In some places it was sufficient 

 in quantity to give the tissue a dark grey appearance. A white 

 granular material exuded from the cut tumour. It was albuminous, 

 and coagulated at once in water. The tissue is a delicate network 

 of connective tissue enclosing* lymph. An extensive system of 

 small blood-vessels runs throughout the tissue. Under the micro- 

 scope no oil was observed in the fluid. 



The surface of the tumour was well supplied with blood-vessels. 

 At the hilum, or part where the tumour was connected to the 

 portion on the other side of the body, there was a small irregularly- 

 shaped cavity filled with a reddish fluid (bl. sp.). There appeared 

 to be a good deal of blood in it. 



The tumour appears to be a lymph tumour. Elephantiasis is 

 caused by the interruption of the lymphatics by Filaria. This 

 seems to be an analogous disease, due to obstruction of the 

 lymphatic vessel. 



The muscles of this fish were also affected in a manner which is 

 not uncommon in the species. The peripheral muscles become 

 infiltrated with oil,* and the fibres swell up. This is analogous to 

 the enriching of the muscles of the salmon with fat, but instead of 

 the oil being distributed throughout all the muscles, it is here 

 limited to a small region. The presence of the oil is detected by 

 the change in the colour of the muscle-fibres. Instead of being 

 translucent, they become of an amber colour. The affected muscles 

 are distributed symmetrically round the trunk. Fig. 161 exhibits 

 a section of the fish. The dotted region indicates the muscles filled 

 with oil. There is normally a strip of so-called red muscle in the 

 lateral-line region. But it may extend in through the trunk 

 towards the vertebral column, and also spread dorsally and ventrally 

 along next the skin. The oil is laid down first in the middle part 

 of the fibre. Fig. 154 represents three myotomes seen from above, 

 The shaded portion indicates the parts infiltrated with oil. A 

 vertical section through the myotomes (fig. 153) shows how thin the 

 affected layer may be, viz., oil. The affected fibres are much swollen 

 (fig. 155). Part of a fibre is shown enlarged in fig. 160. The great 

 increase in thickness due to the oil, which is visible in the form of 

 longitudinal rows of corpuscles, is shown. The transverse stria- 

 tion is hidden ; it is only visible at x. The oil corpuscles are 

 probably located in the little compartments into which the fibrillse 

 are divided by the transverse striatums. The fibrilla? within the 

 muscle fibre appear to become infiltrated before the peripheral 

 fibrillse. Fig. 158 represents a fibre in which the fatty drops could 

 be seen in the deep fibriHa?, while transverse stria? were visible in 

 the surface fibrillar. The extension of the region occupied by red 

 muscle is no doubt due to some interference with the lymphatic 



* I have throughout this part referred to the liquid with which the muscles are 

 infiltrated as oil or fat. That is a description of its appearance. Its true nature 

 was not made out. 



