53 
Structure and Uses of the Spleen . 
This experiment was repeated on another person ; the rhu- 
barb was detected in the urine in 20 minutes. In 2 hours the 
tinge became very faint ; in 5 hours it was scarcely perceptible : 
in seven hours the rhubarb acted on the bowels ; and the urine 
made after that period, became again as highly tinged as at 
first. 
It was suggested by a chemical friend, that the prussiate of 
potash might be a better substance than rhubarb, for the pre- 
sent experiments, since the solution of one quarter of a grain 
in two ounces of water, becomes of a blue colour on the ad- 
dition of the acidulous muriate of iron. 
To determine this point, one quarter of a grain was dissolved 
in two ounces of serum, but no blue colour was produced by 
the addition of the test, nor did this effect take place till the 
quantity of the prussiate was encreased to a grain ; so that 
minute quantities of the prussiate of potash, or at least of the 
prussic acid, may exist in the blood, without being detected by 
adding solution of iron. 
The effects of rhubarb on the urine, and the different parts 
of the blood having been thus ascertained, a third experiment 
was made, in which that substance was employed, and I had 
the assistance of the same gentlemen as in the others. 
O11 November 17, 1807, at 35 minutes past 11 o’clock, five 
drams of a mixture of tincture of rhubarb and water, in the 
proportion of a dram to an ounce, were injected into the sto- 
mach of a dog, whose pylorus was secured. At 20 minutes 
past 1 , two ounces of fluid were brought up by vomiting : ten 
minutes afterwards, another ounce of the mixture was injected, 
as were nine drams more at ± past 4 o’clock. The two last 
portions were retained, and at 8 o’clock in the evening the dog 
was killed. 
