( 383 ) 
b. By the described vulneration of the medulla the secretion of 
urea rose to about double or more. 
c. Sugar could never be detected in the urine after the “prick”. 
d. The osmotic pressure of the urine rises with increased diuresis 
and hence approaches that of the blood serum. 
e. The resistance of the urine for the electric current is increased 
with stronger diuresis. 
/■ From d and e it may already be surmised that the percentage 
of urea has risen with the diuresis. This is confirmed by the expe¬ 
riments. The percentage of urea rose to 3 — 5 times its original value. 
If the filtration theory be true, then, as Starling says: “Mit wach- 
sender Absonderungsgeschwindigkeit (muss) ceteris paribus Beschaffen- 
heit des Harns nach Zusammensetzung, Reaktion und osrnotischem 
Druck immer mehr der des Blutserums minus Eiweisz sich nahern 1 ).” 
The experiments here described afford in my opinion an unexpected 
confirmation of the accuracy of Starling’s thesis and so a probability 
for the accuracy of Ludwig’s explanation of the secretion of the kidneys. 
Mathematics. — “On the stable positions of equilibrium of floating 
parallelepipeda.” By Dr. P. Brandsen. (Communicated by Prof. 
D. J. Korteweg. 
(Communicated in the meeting of October 30 , 1909 ). . 
1- In the following paper will be communicated in short some¬ 
thing about the stable conditions of equilibrium of floating homogeneous 
parallelopipeda. 
Resting on the principle of Lejeune-Dirichlet: “the position 
ln which the potential energy is fninimal is a stable position of 
equilibrium,” we shall have to find positions where the common 
centre of gravity of the floating solid and the liquid is as low as 
Possible. 
From this (see Appell, Traite de mecanique rationnelle, T. Ill, 
03, p. 180—218) the following construction indicated by Dupin, 
can be deduced. 
To find the position of equilibrium of a solid we have to deter- 
mine a surface {G) which is the locus in the solid of the centres of 
gravity of the volumes of liquid, by the immersed parts according 
0 die law of Archimedes (which centres of gravity coincide for a 
l ) Quoted from Metzner (l. c.) p. 242. 
