1901.] Spurge (Euphorbia hiberna, L.) on Salmonoicl Fishes. 63 



vessels of the kidney did not display this difference from the normal 

 condition, which lends further proof of the quite local action of the 

 component of the Spurge which has fatal effects, because the kidneys 

 lie behind the air-bladder and are thus protected from whatsoever may 

 be injected into the abdominal cavity, unless it reaches them by way 

 of the circulation. 



The time taken by the Spurge-extract to be, fatal when injected into 

 the abdominal cavity may be quoted here in order to show that the 

 fatal effects of the Spurge in rivers arise from some action on the gills. 

 An injection of 0*5 c.c. of fresh extract took more than 12 hours to be 

 fatal. The same quantity in 500 c.c. of water would be fatal within 

 less than 2 hours were the fish immersed in it, that is, if it acted on 

 the gills. A stoppage in the gills affects the whole circulation, whereas 

 in any other part the effect is local. 



The experiments recorded in Table II give some notion of the 

 deadly nature of the Spurge. Only in four cases out of many did the 

 fish recover when removed from the Spurge solution to fresh water. 

 In the first two cases the animals were immersed in strong solutions 

 for a short time, too short apparently for the Spurge to have fatal 

 effects, although the inertness of the fish when removed to fresh water 

 showed that the poison had really affected their tissues. The other 

 two cases show that the extract becomes somewhat less deadly after 

 standing for several days, probably because a fungus gradually 

 develops in it and thereby lessens the amount of tannic acid in the 

 solution. 



When the fish are immersed in solutions of pure tannic acid, the 

 effects are similar to those produced by the Spurge-extract. The 

 solutions employed were of 0*01 per cent, and 0*02 per cent, strength. 

 In the former, death occurred within 4 hours, in the latter within 

 2 hours. There was no excitement on immersion, no loss of sensation, 

 nor loss of balance. The gill-covers displayed spasmodic movements 

 and were maintained wider open than in the normal trout, just as when 

 the fish were under the action of the Spurge-extract. Also, when the 

 trout were removed from the solution of tannic acid to fresh water 

 they failed to recover. Post-mortem examination showed that the 

 sloughing of the epithelial covering of the gills was more marked in 

 the case of tannic acid, especially in a 1 per cent, solution, than in the 

 case of the Spurge. A further difference was the absence of any sign 

 that the nervous system was affected. 



A comparison of the times which the tannic-acid solutions and the 

 Spurge-extract solutions took to be fatal, given in Table I, shows that 

 the latter is more rapidly fatal in its action than the supposed per- 

 centage of tannic acid it contains (1 to 2 per cent.) would allow one to 

 expect. A 0*1 per cent, solution of the fresh extract of the Spurge is 

 fatal in less than two hours, and this solution, according to the calcu- 



VOL. LXX. F 



