-240 Transactions. 



To throw further light on the first two effects — viz., mortality amongst 

 yearlings, and pop-eye — lots of ten fish were placed in each of the boxes 

 1, 3, and 4 at the Museum. It was already known that both death and 

 pop-eye occurred in box 2. The result of these experiments was to a 

 certain extent vitiated by the extreme agility with which the fish escaped, 

 even though every care was taken to prevent it. The radium-emanation 

 content was, in the units we have used, as follows : — 



Box No. 1 . . . . . . . . . . 197 



„ No. 2 . . . . . . . . . . 179 



„ No. 3 . . . . . . . . . . 164 



„ No. 4 . . . . . . . . . . 150 



The fish were very kindly supplied to us by the Acclimatisation Society. 

 From the reason given, we are unable to supply any exact data as to 

 niimbers, but it is unquestionable that both death and pop-eye occur most 

 readily in the boxes nearest the well. Whilst this is so, of 10 fish put into 

 box No. 4 on the 3rd September, 1 died on the 6th September, 1 on the 

 14th September, and 1 on the 18th September. We have not recorded a 

 case of pop-eye in box No. 4, though it occurred in box No. 3. 



The fish dying in these boxes were submitted to Dr. Chilton for 

 examination ; and he found clear evidence in some, though not in all, 

 of gas emboli in the gill-filaments, and on pricking the conjunctiva of a 

 fish with pop-eye, two or three bubbles of gas escaped from behind the eye, 

 and the eye resumed its proper and normal position. 



An examination of a pool in the Gardens where large numbers of fish 

 were kept in very close confinement for stripping purposes gave the follow- 

 ing gas content : — • 



C.c. per Litre. 

 Nitrogen . . . . . . . . . . 16-95 



Oxygen . . . . . . . . . . 4-59 



Carbon-dioxide . . . . . . . . . . 2-16 



Temperature, 12*4 C. 



Comparing these figures with box 3 at the Museum, in which on several 

 trials a large number of fish died, and in which one case of pop-eye was 

 developed, it will be seen that less than a cubic centimetre per litre of 

 nitrogen divides the two, and about 0-4 of a cubic centimetre of oxygen, 

 and yet the difference is one of life and death. Whilst this is so, the 

 radium - emanation contents are, in box 3, 164, and in the stripping- 

 pool, 80. 



An attempt was made to determine the nature of the gas liberated from 

 behind the eye in a fish suffering from pop-eye, by means of a spectroscopic 

 examination of it, but without certain result. It is hoped to decide the 

 point definitely later on. 



The whole question is one for biologists and physiologists rather than 

 for physicists ; and the problems suggested to them for discussion are these : 

 (1) Is the diS'erence in the amount of nitrogen sufficient to explain the 

 eSects, of which there are four separate ones ? (2) Are these effects due to 

 an insufficiency of oxygen ? or (3) are the gas emboli in the gill-filaments 

 and the gas behind the eye a secondary effect caused by radium emanation, 

 which is, though present in extremely minute quantities, so extraordinarily 

 active a gas as to be possibly capable of producing the effect if the first two 

 questions should be answered in the negative ? 



