Dr. H. M. Kyle. On the Action of the [June, 2o 7 



table. Here it is only necessary to give analysis of the symptoms and 

 explain how they are caused. 



One of the symptoms frequently displayed by the trout after im- 

 mersion in a solution of the Spurge-extract is great excitement. The 

 animals dash wildly about, and soon or late turn over on their backs,, 

 remaining thus for a long time if the solution is weak, until they die. 

 Of twenty examples, ten displayed these phenomena, but the other 

 ten showed no excitement, and remained in the normal position until 

 within a few minutes of death. This variability was seen both in 

 weak and strong solutions of the extract, and makes it impossible to 

 believe that these symptoms are directly due to the Spurge. This 

 negative conclusion is further strengthened by the fact that those 

 fishes which possess air-bladders, and especially the trout, very readily 

 lose their balance on seemingly slight provocation. Thus, if these 

 trout are placed in water of higher temperature than they have been 

 accustomed to, or even if exposed in a glass vessel to the rays of the 

 sun — many of them will turn over on their backs and remain so until 

 placed in colder water, or until they die. Sometimes, also, if suddenly 

 startled, they display all the symptoms of excitement described above ; 

 and the only conclusion which can be drawn is, that the presence of 

 anything unusual if sufficiently powerful, will induce a state of excite- 

 ment in the trout leading to a loss, temporary or permanent, of the 

 power of balancing themselves. 



This loss of balance seems to arise from an affection of the central 

 nervous system, causing an increased secretion of the gaseous con- 

 tents of the air-bladder, at the same time having an inhibitory effect 

 on the muscular tissue surrounding the opening of the air-bladder 

 into the oesophagus, because it is invariably noticed in those trout 

 which have a period of excitement and then come to rest, exhausted, 

 yet remaining in the normal position, that successive bubbles of gas- 

 escape from their mouths, whereas no bubbles are to be seen in those 

 cases where the trout loses its balance. Why this nervous affection 

 should occur in some cases and not in others is as difficult to explain, 

 as the origin and variabilitj^ of nervous diseases in general. 



Another symptom of the same order is a peculiar gasping move- 

 ment or spasm of the jaws and gill-covers, which is of constant 

 occurrence and increases in frequency the longer the trout are 

 immersed in the solution of the Spurge. But this phenomenon may 

 appear under a variety of circumstances. Professor Mcintosh noticed 

 it whilst experimenting with various drugs upon young salmon, and 

 he found that each spasm was accompanied by a discontinuity in the 

 contractions of the ventricle. It may at times be noticed in the 

 trout when under normal conditions, but occurs more frequently 

 under abnormal conditions — as, for example, after the trout have 

 been startled and excited in any way. It thus may be one of the 



