PHYSIOLOGICAL ACTION OF VENOM OF BLACK SNAKE. 197 
The third limb of the Y tube is connected in the one case to the 
central, and in the other to the peripheral end of a vein by means 
of another rubber tube and suitable cannula. At the end of the 
instrument which is attached to the central end of a vein a piece 
of glass tube bent in the shape of a horse-shoe is inserted in the 
position h. Screw clamps ¢, c’; d, d’, are applied in the positions 
indicated in the diagram. 
Before using the apparatus, A and B were filled, one with air 
and the other with a mixture of gases containing 5 vols. each of 
oxygen and carbonic acid and 90 vols. of nitrogen, and all the 
clamps tightened. The rubber connections between the clamps and 
the bloodvessels were filled either with blood or salt solution, and 
the cannnule tied in their respective vessels. 1 have found it 
most convenient to connect the tube (a) to the peripheral end of 
the femoral vein, and the tube (5) to the central end of the jugular 
vein on the same side. The whole apparatus is inclined at a small 
angle and by relaxing the screws dor d’ and c orc’ and then 
removing the clamp forceps on the veins, blood is allowed to enter 
the tube (2) and trickle down the glass tube A or B which contains 
the mixture of gases, and eventually escape through (5) into the 
tirculation again. The horse-shoe shaped tube of glass (4) is 
necessary in order that it may be seen at once if bubbles of air are 
earried along with the blood and that they may be prevented 
from entering the circulation. There is after a little practice no 
difficulty in preventing this accident. The rate of flow of blood 
through the apparatus could be regulated with nicety by means 
of the screw clamps d and d’. Throughout the experiments the 
: loss of heat to the blood which took place during its passage 
: errough the rubber tubes was minimised by enveloping these 
_ tubes in cotton wool. 
in the blood trickles through, it is spread in a thin layer over 
the interior surface of the tube and so presents a considerable area 
_ “gaseous interchange with the mixture of gases above. This 
: ang : proceeds until the partial pressure of the gases in ane 
oi’ 18 the same as that of the blood. When a sufficient time 
