nimals, under pressures which he was able
to vary at pleasure between 80 mm. and 190 mm. Fifty experiments on dogs
whose blood and kidneys were, during the experiment, kept at 40 deg. C.,
yielded the result that the blood of starving animals induced no secretion
of urine, which on the other hand showed itself in copious quantities where
normal blood was conducted through the kidney. If to the famished blood was
added one of the substances contained as ultimate products of digestion in
the blood, such, for example, as urea, then did the secretion ensue.

The fluid dropping from the ureter contained more urea than did the blood.
That fluid was therefore no filtrate, but a secretion. An enhancement of
the pressure of the blood flowing through the kidney had no influence on
the quantity of the secretion passing away. An increased rate of movement
on the part of the blood, on the other hand, increased in equal degree the
quantity of urine. On a solution of common salt or of mere serum sanguinis
being poured through the kidney, no secretion followed. All these facts,
involving the exclusion of the possibility of a central influence being
exercised from, the heart or from the nervous system on the kidneys, were
deemed by the speaker arguments proving that the urine was secreted by the
renal epithelial cells. A series of diuretics was next tried, in order to
establish whether they operated in the way of stimulus centrally on the
heart or peripherally on the renal cells. Digitalis was a central diuretic.
Common salt, on the other hand, was a peripheral diuretic. Added in the
portion of 2 per cent. to the blood, it increased the quantity of urine
eight to fifteen fold. Even in much less doses, it was a powerful diuretic.
In a similar manner, if yet not so intensely, operated saltpeter and
coffeine, as also urea and pilocarpine. On the introduction, however, of
the last substance into the blood, the rate of circulation was accelerated
in an equal measure as was the quantity of urine increased, so that in this
case the increase in the quantity of urine was, perhaps, exclusively
conditioned by the greater speed in the movement of the blood. On the other
hand, the quantity of secreted urine was reduced when morphine or strychine
was administered to the blood. In the case of the application of
strychnine, the rate in the current of the blood was retarded in a
proportion equal to the reduction in the secretion of the urine.

The speaker