m'intosh, on young salmon. 119 



fibres, for after the cavity is filled by the rapid jerk of the 

 auricle it does not immediately contract, and is thus thrown 

 back a beat. This is especially observed after the auricle 

 has gained greater frequency of action. Occasionally there 

 was marked jerking of the arterial system, very well seen in 

 the branchial coils {i), and indeed throughout. The blood in 

 the aorta appears of a deej^er red than that in the vein, but 

 this is probably due in some measure to the thickness of its 

 coats, since the vein becomes about as dark when it passes 

 beneath the muscular bands. 



When the animal has been reduced to a state of complete 

 paralysis by a large dose it may sometimes be seen that the 

 ventricle contracts only at Avide intervals, while the auricle 

 may be pvdsating 68 to 70 times per minute. The auricular 

 jet scarcely reddens the ventricle, and several are required 

 before the cavity is tinged in the centre ; then the ventricle 

 contracts. Four, five, or even seven, contractions of the 

 auricle ensued before the ventricle acted. In one case it was 

 seen that only every second beat forced the blood through 

 the auriculo-ventricular opening. The blood in the early 

 stage of the dilating ventricle assumed a Y-shaped outline, 

 with the fork directed posteriorly; but after a few more 

 auricular beats this became lost in the general red. In these 

 and other instances in which the ventricle is filled with 

 blood, and just before contracting, it may be observed that 

 processes clij? here and there into the whitish walls of the 

 cavity, showing that even in this early stage the chamber 

 contains muscular bands Avith interspaces. 



If the action of the heart be quickly reduced to 22 by a 

 powerful dose of the poison, and the animal removed to run- 

 ning Avater, the pulsations in some become regular and in- 

 crease in strength, and the circulation throughout the body 

 improves ; but before reaching the stage in which the auri- 

 cular action is twice as frequent as the ventricular an inter- 

 mediate state occurs, in which a pause takes place every 

 sixth or seventh beat. 



When the fish experimented Avith is older, and the yolk- 

 sac Avell absorbed, a A'ery small dose (scarcely a minim) 

 creates urgent symptoms, such as immediate irritation, rapid 

 respiratory movements, gasping, violent muscular tremors, 

 retardation of the circulation, gradual diminution of l)lood in 

 the heart, loss of voluntary motion, and death. Minute ob- 

 serA'ation, however, in such instances is diflicult, on account 

 of the opacity of the animals. 



The muscles of respiration Avere paralysed in common Avith 

 the others, yet one could scai'cely attribute death to this 



