656 THE SECRETION OF URINE. 
periments by Adami, 1 working in Heidenhain's laboratory, lias shown 
that in the frog it is impossible to cut oft' the blood supply to the 
glomeruli by ligaturing the renal arteries. In fact, after this operation, 
fully half of the glomeruli may be injected from the aorta, owing to 
the free anastomoses between the renal artery and the branches of 
the ovarian arteries and the renal portal vein, and it is difficult to 
understand how Nussbaum can have obtained the very definite results 
described by him. These, therefore, in spite of the ingenuity of the 
methods employed, must be discredited in any discussion concerning the 
functions of the various parts of the kidney tubule. 
Experiments of Ribbert. — A bold attempt to experimentally disso- 
ciate the activities of the two portions of the urinary tubule was made 
by Eibbert, 2 who adopted the method of excising as far as possible the 
medulla of the kidney, so as to obtain the glomerular secretion after 
it had passed through only the first convoluted tubules. This opera- 
tion is only possible in animals such as the rabbit, in which the renal 
medulla is made up of one Malpighian pyramid. It was carried out 
in the following way : — One kidney having been exposed from the 
back, was cut in two by an incision at right angles to the long diameter 
of the organ, extending into the pelvis. By means of a gouge, as much 
as possible of the pyramid internal to the boundary zone was removed. 
The two halves of the kidney were then placed together and secured 
by sutures, and the other kidney totally excised. Eibbert found that 
such animals during the next twelve to twenty-four hours secreted a 
much larger quantity of urine than they had previously done. The 
urine was more dilute and much lighter in colour than the urine of 
rabbits under normal conditions. No analyses, however, of the fluid 
were made. Eibbert interprets these results as confirming Ludwig's 
hypothesis. But apart from the increased quantity, which does not 
seem to me to be definitely established by Eibbert's experiments, the 
production of a more dilute urine would be expected on either 
hypothesis, whether we assume with Ludwig that the tubules absorb 
water from the urine, or with Heidenhain that they excrete solid 
substances into the urine. 
Experiments of Bradford. — The very insufficient description of 
his experiments given by Eibbert might incline us to discredit them 
altogether, were it not that somewhat analogous results have been 
obtained by Bradford. 3 This observer found that extirpation of one 
kidney, combined with excision of a large wedge-shaped piece from the 
other kidney, might bring about one of two results — 
1. If the amount of kidney substance left amounted to one quarter 
of the weight of the two kidneys, the animals (dogs) lived a considerable 
time, but suffered from hydruria, i.e. the quantity of urine excreted was 
largely increased, but the excretion of urea remained unchanged, so 
that the urine was much more dilute than before. 
2. If the amount of kidney left was less than one-sixth of the total 
kidney substance, polyuria w T as produced, i.e. a large increase in the 
excretion of water as well as of urea. This increased production of urea 
was due to a rapid wasting of the proteid constituents, and especially of 
the muscles of the body, so that the animals died in a short time in a 
1 Journ. Physiol., Cambridge and London, 1885, vol. vL p. 382. 
2 Virchoiu's Archiv, 1883, Bd. xciii. S. 169. 
3 Proc. Boy. Soc. London, 1892, vol. li. 
