1901.] Spurge (Euphorbia hiberna, L.) on Salmonoid Fishes. 55 



extract has no action on muscular tissue when treated in the above 

 way. Injection of the extract into the muscle was not attempted. 



Although both the motor nervous and muscular systems are not af- 

 fected, the same cannot be said for the sensory nervous system. Very few 

 experiments were made on this point, but they seem sufficient to show 

 that the sensory nerve-tracts are slightly paralysed at some part of 

 their course. The reflex time of two pithed frogs, which were allowed 

 to remain in this condition for some hours after the operation to allow 

 them to recover from the shock, was found to be several seconds 

 greater on the average after injection of the Spurge-extract than before. 

 And again, two similarly treated frogs responded to weaker electrical 

 stimuli before injection of the extract than after. Taken in conjunc- 

 tion with the previous experiments on the motor system, these results 

 show that the sensory nerves or central nervous system are in some 

 way affected. 



The quantity of volatile substance which is present in the fresh 

 aqueous extract, though it produces a slight paralysis of sensation, is 

 not sufficient to account for the fatal effects which the same extract 

 has on fishes, and also on frogs when treated in a certain manner. 



If a pithed frog's lung be dissected out and irrigated with normal 

 saline solution, the circulation in the capillaries may be watched for a 

 long time. When now a few drops of the Spurge-extract are placed 

 on the lung, a great and almost immediate change is seen. The capil- 

 laries shrink visibly, the blood corpuscles are pressed backwards into 

 the arterioles and sway to and fro with each beat of the heart. The 

 heart-beats become slower and more protracted if the Spurge irrigation 

 is continued. The whole lung contracts to half its previous size, and 

 in the larger vessels which also contract, a condition of stasis sets in, 

 ending with the death of the frog within half an hour of the operation. 

 If the mesentery, and not the lung, be chosen for examination, a 

 similar result is obtained, but this has the additional advantage of 

 showing that the action is quite local. If a small portion of the intes- 

 tine is irrigated with the extract, the blood ceases to flow in the 

 arteries leading to that part, but not in the neighbouring ones. 



The effects here described are obviously due to the tannic acid, and 

 the application of the latter directly produces the same result. Even 

 a. weak solution, 0*01 per cent, of tannic acid (1 in 10,000), has a 

 marked effect upon the capillaries, whilst a 1 per cent, causes stasis 

 almost immediately. Further, when the lung is irrigated with normal 

 saline solution after treatment with 0*01 per cent, of tannic acid, cir- 

 culation is gradually re-established, but not so after 1 per cent. The 

 latter case resembles that of the Spurge-extract, for irrigation with 

 normal saline solution after treatment with the fresh extract enables 

 the circulation to be maintained in the vessels which had not become 

 constricted, but cannot revive it in the others. 



