46 
POISONS : THEIR EFFECTS AND DETECTION. 
[§ 34 - 
The heart of the frog, of the turtle, of the tortoise, and of the shark will beat regu¬ 
larly for a long time after removal from the body, if supplied with a regular stream 
of nutrient fluid. The fluids used for this purpose are the blood of the herbivora 
diluted with common salt solution, or a serum albumin solution, or a 2 per cent, solu¬ 
tion of gum arabic in which red blood corpuscles are suspended. The simplest 
apparatus to use is that known as “ Williams’.” Williams’ apparatus consists of two 
glass bulbs (see diagram), the one, P, containing nutrient fluid to which a known 
quantity of the poison has been added ; 
the other, N, containing the same fluid 
but to which no poison has been added ; 
these bulbs are connected by caoutchouc 
tubing to a three-way tube, T, and each 
piece of caoutchouc tubing has a pressure 
screw clip, V' and V ; the three-way tube 
is connected with a wider tube contain¬ 
ing a valve float, F, which gives freo 
passage of fluid in one direction only, that 
is, in the direction of the arrow ; this last 
wide tube is connected with a Y-piece of 
tubing, which again is connected with the 
aorta of the heart under examination; 
the other leg of the Y tube is connected 
with another wide tube, X, having a 
float valve, F 2 : the float containing a 
drop of mercury and permitting (like the 
float valve F) passage in one direction 
only of fluid, it is obvious that if the clip 
communicating with N is opened and the 
clip communicating with P is closed, the 
normal fluid will circulate alone through 
the heart; if, on the other hand, the P 
clip is open and the N clip closed, the 
poisoned blood will alone feed the heart. 
It is also clear that by raising or depress¬ 
ing the bulbs the circulating fluid can be 
delivered at any pressure, high or low. 
Should a bubble of air get into the tubes, 
it can be got rid of by removing the cork 
at S and bringing the fluid up to the level 
of the top of the aperture. The observa¬ 
tion is made by first ascertaining the 
number and character of the beats when the normal fluid is circulating, and then 
afterwards when the normal is replaced by the poisoned fluid. A simpler but less 
accurate process is to pith two frogs, excise their respective hearts, and place the 
hearts in watch-glasses containing either serum or a solution of common salt 
(strength 0-75 per cent.) ; to the one heart is now added a solution of the poison 
under examination, and the difference in the behaviour and character of the beats 
noted. 
The phenomena to be specially looked for are the following :— 
1. The heart at the height of the poisoning is arrested in diastole. 
2. The heart at the height of the poisoning is arrested in systole. 
1. Arrest in Diastole. —Tho arrest may be preceded by the contractions becoming 
weaker and weaker, or after the so-called heart peristalsis; or it may be precoded by 
a condition in which the auricle shows a different frequency to the ventricle. 
Tho final diastole may bo the diastole of paralysis or the diastole of irritation. 
Tho diastole of irritation is produced by a stimulus of tho inhibitory ganglia, and 
only occurs after poisoning by the muscarine group of poisons. This condition may 
