VOL. XXVI.] PHILOSOPHICAL TRANSACTIONS. 463 



I have several times observed in the exceedingly small veins or capillary vessels, 

 a little rising or sjjtelling occasioned by a stronger motion of the blood, which I 

 now tirmly conclude, to proceed only from the sudden motion or running of the 

 blood through the valves : I have also observed, that in sudden frights, and 

 otherwise, one feels such motions at the end of one's fingers, just as if there 

 were valves likewise in them, through which the blood gushes ; but these sort 

 of motions, I suppose, do only depend on that quick motion made by the 

 blood, when it runs through the valve in the arm by the hand, to which we 

 give the name of a pulse. 



In the month of September, having opened an eel, the diameter or thickness 

 of which was about an inch and a half; and having laid open the heart, I could 

 not discover that part which receives the blood out of the great vein in order to 

 bring it into the heart. But that I might the better discover that part, I pre- 

 pared a little glass tube, and put it into the great vein at a little distance from 

 the heart, and then blew some air into the said vein, as much as might take up 

 the space of about half a pea: this air passed through the great vein into a little 

 bladder that lay on the side of the heart, and no sooner was the air got into that 

 bladder, but it first contracted, and then dilated itself, so regularly, and in such 

 a manner, that when the heart contracted itself, just as if it were going to pro- 

 trude its blood, the said little bladder with air in it was dilated, and continued 

 in such a motion above 5 full hours together : though indeed in the last hour it 

 was so faint, that one could but just perceive it; and as for the heart, its mo- 

 tion was discontinued. 



I also took a pike-fish, about 2 feet long, and opened it immediately while it 

 was in its full strength of life, and observed not only the motion of the heart, 

 and the regular motion of that part which receives the blood, and brings it into 

 the heart, but also the motion of that other part, which receives the protruded 

 blood from the heart, and carries it gently into the arteries. 



PI. 10, fig. 23, shows the heart of a pike; depa represents that part into 

 which the blood is brought from the veins ; and cdg that other part which re- 

 ceives the blood from the heart, to carry it into the arteries. Now when the 

 heart receives the blood which is conveyed into it, it dilates to its utmost 

 roundness ; and then that vessel represented by adef at that very instant 

 collapses; and discharging its blood into the vessel cdg, this becomes distended 

 by the sudden pouring in of the blood ; snd no sooner is it so dilated, but it 

 contracts again, that it may force the blood into the arteries. In short, when 

 ADEP is contracted, and throws the blood into the heart, this is dilated ; and 

 when the heart contracts and discharges the blood, cdg is dilated : and these 

 three several motions happen in so short a time, and are performed so regularly, 

 that it is quite surprising : and from hence we cannot but conclude, that such a 



