42 Part III. — Twenty-eighth Annual Report 



in the original ulcers, and seen in the smear preparations and in the hanging 

 drop preparations, in which they were actively motile. 



After the death of the haddocks and whitings in the tanks, the tanks were 

 emptied and cleaned out, but the water they contained was inadvertently 

 allowed to get into an outside pond in which there were about 150 plaice. 



In the beginning of September 1908, 193 plaice arrived from the Moray 

 Firth, and, on being placed in the pond amongst the other plaice, it was 

 then discovered that 58 of the 150 plaice in the pond were dead, and were 

 removed. On the 23rd October, 267 more plaice arrived from the Moray 

 Firth and were placed in the pond ; and it was shortly after that date when 

 129 more dead plaice were discovered and removed from the pond. On the 

 27th November, 284 more plaice were received from the Moray Firth and 

 placed in the pond, and up to 26th December 1908, 13 more dead plaice 

 had been removed. That is, during four months 200 plaice have died in 

 this pond. 



The fish from the Moray Firth, on careful examination, showed no 

 evidence of any disease. 



After frequently examining these fish, I could come to no other conclusion 

 than that they were suffering from the same disease as that which appeared 

 in the case of the haddocks and whitings. The superficial ulcers were of the 

 spreading and sloughing type, and presented precisely the same characters as 

 already described in the former fish. They showed the same irregular 

 distribution on neck, back, and tail, but were very seldom seen on the 

 ventral surface. They commenced in paling and desquamating spots, and 

 spreading rapidly to form large ulcerated areas, often one to two inches in 

 diameter. The edges of the ulcers were deeply undermined, the base often 

 extending down to the muscular tissue and covered with broken-down tissue. 

 But here the base of the ulcers often presented a very injected appearance, 

 and there appeared to be a decidedly stronger reaction on the part of the 

 tissues against the invading micro-organisms than what appeared in the case 

 of the haddocks and whitings. This may be due to a better blood supply in 

 the case of the plaice, which on the whole are hardier fish than the round 

 edible fish such as haddocks and whitings ; and although difficult to state 

 definitely, yet there has to be kept in view the probability of variation both 

 in the direction of diminution of the virulence of the attacking micro- 

 organisms, and also in the powers of resistance of these difi'erent classes of 

 fish. 



Bacteriological Examination. 



Two of the plaice were conveyed to Marischal College while still alive, and 

 a bacteriological examination made precisely in every detail as in the case of 

 the haddocks and whitings. Hence I will not repeat the various processes, 

 but state the results. 



From all the lesions examined by smear and hanging-drop preparations, 

 rod-shaped and vibrio-like micro-organisms were present. Cocci Avere also 

 present and strongly Gram positive. 



From both fish, by the' methods already described, typical Bacillus Coli 

 were isolated by means of cultural media and subjected to the same confir- 

 matory tests. 



From the blood pure cultures of cocci were obtained. These were 

 subjected to the usual tests for the staphlococcus pyogenes aureus. 



The cultures from the peritoneal fluid were again negative. 



Sections were made as already described. These showed the same appear- 

 ance as in the case of the haddocks and whitings. 



Again, in none of the cultural preparations nor in sections did the vibrio- 

 like organisms appear which were always seen in smear preparations made 

 from the lesions while the fish were alive. 



