attained this condition form a well-regulated school and consequently 

 there is very little opportunity for them to be injured by collision 

 or rubbing together^ Furthermore , as has already been stated, the 

 internal injuries which are received at the time of capture or when the 

 fish are placed in the bait-tanks will after a few days either result 

 in death or will be naturally cured, and therefore the usual thing is for 

 bleeding fish to gradually disappear and for the death rate to abruptly 

 decline when a certain amount of time has passed after the fish have been 

 placed in captivity. 



However, when several weeks have passed after the fish have been 

 placed in the live-pound, red spots due to bleeding, called by the 

 fishermen w red rust", appear under their skin (Figure 12) , If fish on 

 which these red spots have appeared are carefully examined, it is clear 

 that in most of them it is a matter of simple subcutaneous bleeding and 

 that the internal organs are completely unnarmed, but the peculiarity of 

 this condition is that most of the fish die of just this subcutaneous 

 bleeding. From this fact it can easily be gathered that this bleeding 

 is of a different sort from that described earlier as due to force. 

 Since I have not yet had an opportunity to study this phenomenon, I 

 cannot speak with conviction, but in view of the fact that these symptoms 

 present certain points of resemblance to the Morbus macula sus Werlhofi^o) 

 that occurs in humans and other animals, it is thought tnat it cannot be 

 far wrong to .consider these red spots as a type of pathological damage to 

 the vascular system under certain external conditions. 



Death from Excessive Production of Air Bubbles 



On the occasion of an experiment in holding bait sardines in the 

 bait tanks of the Fuji Maru during a three-day period beginning July 24, 

 1931, an imperfection in the intake of the water pump caused the produc- 

 tion of a great number of bubbles, and at the same time a large number 

 of dead fish appeared, 1) When these dead fisn were carefully examined, 

 items that deserve mention as impressions obtained directly after the 

 fish died are the fact that almost, all of the dead fish had a great many 

 of the above-mentioned small air bubbles on the surface of their bodies 

 and on their gill lamellae and gxll-rakers, and tnat rather conspicuous 

 bleeding could be seen at their snouts, eyeballs, and under their skins. 

 Particularly worthy of note is the fact that the free oxygen did not 

 reach the saturation point (rather there was somewhat of a deficiency) 1), 

 and the fact that there were no air bubbles produced in the eyeballs or 

 under the skin, which facts testified eloquently that the cause of death 

 was not bubble disease. In other words, the cause of these deaths must 

 be sought elsewhere than in bubble disease, Kimura^/ recently has kept 

 sardines in a bait tank in which great quantities of bubbles were produced 

 experimentally and has observed the great number of deaths which resulted. 

 He concluded that the cause of these deaths was the injuries resulting 

 from the disruption of the swimming of the sardines as the bubbles rose 

 in the tank, Ishii30) p using goldfish as material, conducted a roughly 

 similar experiment and found that air bubbles of a radius of 0,03 cm or 



43 



