156 TRANSACTIONS LIVJEEPOOL BIOLOGiCAL SOCtEtY. 



?) cm. in diameter, witli a well marked edge and a red 

 injected base. The lesion commences as a small intiamed 

 area of skin; this increases in size and ultimately the 

 skin breaks down to form an ulcer which gradually 

 enlarges. As a rule more than one ulcer are present, but 

 they are never numerous. The fish dies eventually in an 

 emaciated condition, but infected fish have been observed 

 to feed freely, and even badly infected fish may retain 

 their muscular strength to a surprising extent. 



Microsco])ically, a section through an ulcer reveals 

 great destruction of tissue, the base being covered with 

 debris. Beneath this are many swollen capillaries filled 

 with blood corpuscles, accounting for the injected 

 appearance which the base presents to the naked eye. 

 Xo bacteria were to be seen in the tissues. In the outer 

 layer of dead cells and debris were numerous slender 

 Gram-negative bacilli; these, however, we regard as 

 coming from outside, and probably not pathogenic. 



Bacteriological Investigation. 



The material for this investigation was derived 

 from : — 



(1) A fish (I) found dead in the ])ond and sent to 



Liverpool, examined when two days dead. 

 Cultures were made on to nutrient gelatine 

 from heart blood, liver, and from a large ulcer. 



(2) Cultures were made by Dr. Da kin at Port Erin 



(a) from the ulcers of two living fish (II and 

 III) on gelatine, and (b) from the heart blood 

 and liver of the same two fish, also on gelatine. 

 All these cultures were at once despatched to 

 Liverpool. 



(3) A sample of water from the ponds. 



