284 MR. H. F. BAXTER’S EXPERIMENTAL INQUIRY AS TO THE EXISTENCE 
der, the former positive 5° ; the electrode in contact with the bladder was then 
placed on the surface of the intestines ; blood slightly positive. 
Experiment 6. — Rabbit. Prussic acid dropped on the eye. Between the bladder 
and left renal vein ; the latter positive 3° : tke electrode in contact with the vein was 
then placed on the surface of the intestines in the neighbourhood of the kidney; the 
electrode in contact with the bladder was now positive, slightly. The circuit be- 
tween the vein and bladder was reformed ; no effect. Between the right renal vein 
and bladder ; no effect. 
Bladder full: urine acid to litmus. 
To what other conclusion can we arrive at, than that, during urinary secretion, the 
hlood and urine are in opposite electric states ? The effects are but small, certainly, 
amounting perhaps only to 3° or 4° ; but such as they are they indicate the blood to 
he positive. Considering the small size of the organ, the nature of the secretion, 
acid, and the transient effects that are produced, we may feel some surprise at 
obtaining such satisfactory evidence. 
In judging of the results upon the needle, we must take into consideration the act- 
ing points in the circuit; we have at least three acting points in the circuit; viz. at 
the point of secretion, and at the two electrodes. Although we are led to suppose 
that the current consequent upon the actions which occur at the point of secretion 
and those which occur at the electrode in contact with the blood assist eaeh other, 
nevertheless the current consequent upon the actions which occur at the other elec- 
trode may be of such a nature as to counteract the effects of the two former, de- 
pending, in a great measure, upon the nature of the secretion. Hence we should be 
led to very erroneous conclusions if we judge merely from the effect upon the needle, 
either as to the force of the current, or its origin. We have also some reasons for 
supposing that the flowing of the blood through the organ would have some in- 
fluence, acting by convection'^ or carrying power. We might also add, that the very 
circumstance of a difference being observed, as to the amount of deviation of the 
needle in the different organs, would indicate that the effects cannot be due to one 
and the same cause, for instance, to thermo-electric effects. 
§ 3. On the manifestation of Current Force during Mammary Secretion. 
We have, unfortunately, only one experiment ; the results however may be con- 
sidered of some value. 
A Cat. Prussic acid, swallowed. Unaware at the time that the cat was suckling, 
one of the mammary glands was divided whilst opening the walls of the abdomen. 
One electrode was placed in contact with the milk, the other in contact with the 
blood flowing from one of the mammary veins ; blood positive 8°. 
We should not be justified in coming to any definite conclusion from the result of 
one experiment, and therefore defer making any remarks. 
* Faraday, Experimental Researches, vol. i. p. 496. 
