ON HEAT GENERATED IN THE HLOOD. 141 



amount of heat as the result of oxygenation of the blood. The amount of 

 heating in a given time depended upon several important factors, as the dif- 

 ference bet-sveen the temperature of the blood in the experimental vessel and 

 that of the surrounding air, upon the amount of blood contained in the appa- 

 ratus, and the space through which the vessel was moved during its agitation, 

 no less than upon the number of the agitations. 



To describe, or even to give the results of a series of experiments so emi- 

 nently unsatisfactory, woiild be a mere waste of time ; it will be sufficient 

 for me to state, however, that I clearly came to the conclusion that, like those 

 who had preceded me, I had obtained no positive proof of the heating of 

 blood when it absorbs oxygen, there having been as great a heating when 

 water as when blood was experimented upon. 



In commencing new experiments this year, I did so with the conviction 

 that, in order to obtain results of any value, my apparatus shoiild be so con- 

 structed and my experiments so conducted as to preclude the possibility of 

 any appreciable rise in temperature resulting from the mechanical work of 

 shaking. Then I decided upon discarding thermometers, and making use of 

 thermo-electric junctions of great delicacy. 



The galvanometer employed in the research was one resembling one of 

 Sir Wm. Thomson's older forms, constructed especially for Professor Tait, 

 every possible precaution having been taken to avoid a trace of iron in 

 the coils and framework. The wire was drawn through agate plates 

 from electrolytic copper, covered with white silk and formed into four coils, 

 each adjusted to produce the maximum effect with the least resistance, 

 those parts of the coils nearest the magnets being made of finer wire. 

 The astatic system vibrated under the earth's force once in eight seconds ; 

 but as this was much too delicate for my purpose, I placed near the in- 

 Btriiment a bar-magnet, which reduced the period of vibration to 3^-4. 



The thermo-electric junctions which I employed were made by twisting 

 very thin iron and copper wire together, the free ends of the copper wires 

 being immersed into the mercury pools of a very simple form of commu- 

 tator placed in the circuit, which enabled me, with the greatest ease, to 

 reverse the current flowing along the wires. 



The apparatus actually employed in my experiments consisted of an 

 upper glass vessel, which I may call the blood reservoir, to which was con- 

 nected a lower vessel, also of glass, and in which the blood, wliich was the 

 subject of experiment, could be brought in contact Avith the gases which 

 were intended to act upon it. 



The iipper vessel was a glass bulb of a pyriform shape, and had a capacity 

 of about 150 cubic centimetres. Above and below it was drawn out, so as to 

 present two tubes, the upper of which was bent at right angles and furnished 

 with a piece of india-rubber tubing, which admitted of being closed by a clamp, 

 whilst the lower was furnished with a very accurately ground stopcock. In 

 the side of the bulb was a round tubulature, which could be closed with a cork, 

 through which passed a thermo-electric junction. The lower, or mixing- 

 vessel, was cylindrical in shape, and possessed four apertures. The upper one 

 was closed by a cork, bored so as to allow of the passage of a glass tube, 

 attached above by means of an elastic tube to the stopcock of upper vessel or 

 reservoir, and made of such a length as to reach to the bottom of the mixing- 

 vessel. N^ear the upper aperture was a second lateral one, into which a 

 glass tube had been fused. This glass tube could be connected, by means of 

 a metallic tube and stopcocks, eitlier with a Sprengel mercurial aspirator or 

 with an oxygen or hydrogen gasometer. A third lateral aperture waa 



