16 Fishery Board for Scotland. 



system, which either arrests the abstraction of the lymph from the 

 muscles, or causes it to be deposited in them. 



The fatty infiltration is often more extensive in the tail region 

 than it is anteriorly. It would seem to proceed from behind 

 forwards. 



A saithe in which the swim-bladder was partly filled with a greasy 

 dark-red mass exhibited the extended fatty infiltration of the 

 muscles. Posteriorly the bladder was completely filled up. The 

 dark-red mass seemed to be mainly blood corpuscles. When it was 

 diluted with water, minute fatty (?) granules and some long clear 

 crystals were made out. This material occurred also in loculi 

 between the coats of the swim-bladder. Its wall was papillose in 

 one part. The fatty infiltration of the muscles was not so extensive 

 as in the preceding case, and it was greater behind the second 

 dorsal fin than in the pectoral region. In the pectoral region none 

 of the red muscle extended to the vertebral column. 



When a saithe which is much infected with the symmetrically- 

 extended oil infiltration of the muscles is filletted the flesh may be 

 found to be very prominently discoloured. This is observed 

 sometimes in the tail region. The infected muscles are of a brown 

 or dirty cream colour, and are readily distinguished among normal 

 colourless muscles. They appear on the edge and along the middle 

 of the fillet. When the fish is salted and dried the strips which 

 traverse the trunk longitudinally are still prominent, and form a 

 blemish. It is referred to as grease. In connection with one infected 

 fish, little larva?, like little diatomes, were observed. 



A fish which showed the brown muscles in the tail region had a 

 little mass of decayed matter next the hsemal spines. It probably 

 indicated the disintegration of infected muscles. 



A saithe had tumours just under the skin, near the bases of the 

 caudal fin-rays. Thev were present in both dorsal and ventral 

 sides. The flesh was diseased and broken up, but dry. None of 

 the tumours seemed to be discharging through the skin. 



Sporozoan Infection of Muscles. 



An oval tumour* measuring about 3f inch (9'5 cm.) in greatest 

 diameter was found in the trunk muscles of a catfish (Anarrhichas 

 lupus). It was solid. On cutting into the tumour a whitish fluid 

 exuded. The tumour was simply a mass of swollen muscle fibres. 

 The swelling of the fibre was due to the presence inside it of a 

 smaller or greater quantity of sporoblasts. The sporoblasts are 

 apparently loosely arranged in the cavity formed by the separation 

 of the fibrillas (fig. 59a). The collection here represented (fig. 59a) 

 measured about 1 mm. in diameter, and contained about 30 sporo- 

 blasts. Another oval collection was 12 mm. long. Sometimes 

 the greater part of the length of the fibre is occupied by the 

 sporoblasts. The fibres thus become tubes. The swollen fibres 

 were either white or brown in colour. The former, the recently- 

 infected fibres, were situated in the periphery of the tumour; the 

 central region was occupied with brown fibres. A white fibre is 

 shown in natural size in fig. 62. When such a fibre is teazed the 



* Presented by Messrs. Sinclair & Robertson, Aberdeen. 



