670 
PROFESSOR H. N. MARTIN ON THE INFLUENCE OF VARIATIONS 
of f and f ' must be above the level of the exit of q. To secure this, both flasks, C 
and D, are suspended by cords r, r', which support each flask and its water-jacket. 
These cords pass over pulleys borne on a framework, H, I, J, K, attached to the roof 
of the warm chamber, and each passes at its distal end round a fastener, s ; by means 
of these cords the Mariotte’s flasks can be raised and maintained at any desired 
level within the warm chamber. In the series of experiments here described both flasks 
were raised to the same height, although in fig. 1, C has been drawn lower than D 
for the sake of showing their connexions more clearly in the drawing. 
To fill the syphon connected with C, the stopcock h and the clamp g are closed; 
the clamp i is left open, as is the stopcock l (Plate 48, fig. 2), while l' is kept shut. 
Then q (fig. 1) is opened, and suction applied to the end of y ; blood then flows out 
of C through /, while air enters through e ; and this blood is supplied to y under 
constant pressure. 
The cock q is now closed, as also Ti and the clamp g. The clamp % is left open, the 
stopcock l (Plate 48, fig. 2) closed, and l' opened. When q is now once more opened 
and suction applied to y, blood from D passes out by the tube // and reaches q through 
the tube n (fig. 1). D now, like C, behaves as a Mariotte’s flask, and supplies 
blood to y under a constant pressure. If both flasks be raised to the same height 
above the level of the superior vena cava, with which y (as will be described imme¬ 
diately) is connected, we can supply a heart with blood from either flask at will. 
When the stopcock l (Plate 48, fig. 2) is open and V closed, the heart is fed from the 
flask C; when l is closed and l' opened, the blood is derived from D. 
The flasks and the syphon tubes are filled as above described before the operation 
on the Dog is commenced, and the stopcocks so arranged (l open and V closed) that 
on opening q blood will be drawn from C. 
The water-jackets around each flask being filled, the gas burners under the trough 
which supports the warm chamber are lighted. From time to time q is opened, and 
blood from C let flow through it. When the temperature of this blood, as indicated 
by the thermometer p, is about 37° Cl, the gas is turned low and the operation on 
the Dog, described above, is proceeded with. While the flasks are warming g and g' 
are left open to allow some of the air in each flask to escape as it becomes expanded 
by the heat. Just before transferring the animal to the warm chest, g is screwed up, 
but g left open; h' is also opened, and care is taken that h is shut. Under these 
circumstances C supplies blood to y when q is opened, while D (only one-fourth filled) 
is cut off from all connexion with q but is ready to receive any blood poured into it 
from the funnel F, or flowing to it through the tube L. 
When the animal is transferred to the chamber the portable Mariotte’s flask 
(Plate 48, fig. 3) is carried along with it by an assistant, and still supplies the heart 
with blood. A bit of brass tubing, u (fig. 1), inserted into the lower end of the tube, t, 
is now connected with the distal end of the piece of rubber tubing, v (Plate 48, figs. 
1 and 3), attached to the distal end of the aortic cannula. The clamp w is then opened 
