sin, 
1885.] Fhysiology. 417 
nitric acid. Urea is thus decomposed into equal volumes of car- 
bonic acid and nitrogen which were easily estimated. 
It appeared from these experiments that the blood of the hepatic 
veins, splenic veins and the portal vein contains always more 
urea than the blood of the carotid artery, whence it is concluded 
that the abdominal viscera are the seat of continuous urea forma- 
tion. 
There was no notable difference in urea content between the 
blood coming from the head or the different members and that 
blood which entered those parts. . 
The chyle mixed with lymph drawn from the thoracic duct 
after death was always found richer in urea than either venous or 
arterial blood. . i 
The difference between the urea content of venous and arterial 
blood was much more marked in animals during the digesting 
than in the fasting condition. This agrees with the statement of 
Becker & Voit, who found the’excretion of urea much increased 
during digestion. 
It may be said that these observations are difficult to reconcile 
with the well founded belief that the liver is the principal organ 
for the formation of urea in the body.— Fourn. de l Anat. et Phys., 
1884, p. 317. 
N THE SPECIFIC ENERGY OF THE NERVES OF THE SKIN.—The 
underlying facts of Joh. Müller's generalization that the nerves of 
special sense, as the optic, auditory, gustatory, filaments are en- 
dowed with specific energies cannot be disputed. What is meant 
is that any kind of stimulus whatsoever applied to the optic nerve 
arouses the sensation of light, every irritation of the auditory 
nerve gives rise to the sensation of sound, &c. The characteristic 
quality of these sensations depends not at all upon the peculiarity 
of the sensory nerve, but is determined wholly by the physiologi- 
cal properties of the nerve cells which receive the sensory impulse. 
From the skin, as a sense organ, we receive impressions 
that arouse in us at least two different kinds of sensations, those 
of pressure and of temperature, and it is an important question 
whether the impulses giving rise to these different sensations pro- 
ceed along identical nerves which reply in a different manner to 
differences in the quality of the stimulus, or whether the nerves 
of the skin are functionally differentiated in such a way as to call 
forth specific sensations without regard to the character of the 
stimulus. Weber believed that sensations of temperature and of 
Pressure were modifications of the same sense, depending upon 
the amount of energy aroused in the sensory nerve. Physiological 
analogy throws doubt upon this interpretation, and recently Blix 
has produced evidence which supports the view that the vane 
sensations aroused by excitement of the skin are as truly specific 
and due to the excitement of distinct nerves, as is the case with 
the other special senses. Blix used as stimulus the faradic elec- 
VOL, XIX.—NO, IV. 
