1901.] Spurge (Euphorbia hiberna, L.) on Salmonoid Fishes. . 61 



results of the nervous affection mentioned in the previous paragraph. 

 Whilst these spasms therefore arise from the presence of the Spurge 

 and may be called a secondary effect, they cannot be considered as 

 characteristic of nor as directly due to its action. 



Another symptom which observation, if confined to the action of 

 the Spurge on trout, might lead one to think diagnostic, is the con- 

 stant shedding of mucus from the mouth and skin. And one is the 

 more ready to admit this, seeing that tannic acid, which has this effect, 

 plays an important part in the action of the Spurge. But if trout 

 are placed in clean water in a glass vessel immediately on capture, it 

 will be noticed, after they have calmed down from their excited con- 

 dition, that the water contains an abundant quantity of stringy 

 mucous material. The shedding of mucus seems to occur very readily 

 in salmonoid fishes, perhaps in all, and may be a symptom of the 

 nervous excitement into which the animals are thrown. Again, the 

 change that comes over the breathing may be due to the same cause. 

 The frequency of this is increased during the first few minutes, but 

 later falls below what it was to begin with. In the young post- 

 larval trout, it was noticed that this occurred synchronously with a 

 rise and fall of the pulse-frequency. 



Only on two occasions was any sign given that the digestive system 

 was interfered with. In these cases the trout, after being immersed 

 for some time in a solution of the Spurge, vomited the contents of 

 their stomachs. This again seems to arise from the derangement of 

 the central nervous system already mentioned. 



Excluding these cases there are still one or two symptoms which 

 seem to display the direct local and distant effects of the Spurge, 

 and though separately each may arise from other causes, yet taken 

 together they seem to be characteristic of the action of the Spurge. 



When the trout have been immersed for some time in the solution 

 of the Spurge, it is noticeable that the gill-covers do not close com- 

 pletely over the gills, and that the latter can partly be seen even 

 when the former should be quite closed. Further, the gills themselves 

 appear swollen and of a brighter scarlet than under normal conditions. 

 Post-mortem examination did not show any great difference from 

 the normal. Sometimes a portion of the gill filaments would be 

 injected with blood, showing that inflammation had been present there, 

 but usually the naked-eye appearance was quite normal. In sections 

 the poisoned specimens showed considerable disintegration of the 

 mucus epithelium of the gills, rupture having apparently taken place 

 in the underlying connective tissue, so that the capillaries which 

 remained intact were left denuded. This was not present every- 

 where, but was nevertheless distinct from the normal condition. The 

 capillaries also were much contracted and of smaller calibre than is 

 usually the case. Further, though this difference from the normal 



