416 Scientific Intelligence. 
tube into which the quicksilver rises in obedience 
to atmospheric pressure. For each membrane the 
in the tube has reached its maximum elevation, and 
remains for example in fig. 2 at d, if the part a be 
placed in a vessel of water, the latter is pressed 
readily through ee membrane, and the mercury 
falls for example, to d. 
It follows ioc icads that water may be forced 
through the pores of a membrane at a much lower 
pressure than air. And hence the following ex 
periment may be deere me When a hans tube, bent as 
ith w: 
Fig. 3. Fig. 4. 
with membrane, (this is most 
easily arranged under water,) 
and the one extremity exposed 
‘0 evaporation, while the oth- 
er is immersed in solution of 
salt, or gall, or sugar, the ves- 
‘sel will gradually become ex- 
hausted of its liquid, and the 
tube = esi co This 
pure water would go to noe 
water; but here where ev 
oration takes place, the ie water passes into the tube to pure water. 
But it is not only salt-water, but oil goes under these circumstances 
with readiness hemos al the bladder, and fills the tube in process 2 time 
ate ek wit 
4 exhibits an apparatus where the fluid passes from the vesse essel 
a i ‘the tube 8 throu rough nine membranes. (They are bits of tube clo- 
sed we membranes, and evininatdl through India rubber with the el- 
bow 
The employment of these results upon the processes in the animal 
body, scarcely requires a more detailed explanation. 
The s Sithace of the body is the membrane, from which evaporation 
goes constantly forward. In consequence of this evaporation, all art 
fluids of the body, in obedience to atmospheric semen experience 
_ motion in the direction heh the evaporating surface. This !s 
ously the chief cause of the passage of the nutritious fluids through the 
walls of the blood-vessels, ak the cause of their distribution through 
ody. e know now what important functions the skin (and — 
fulfill through et se It is a condition of nutrition, and t 
“of ir upon the health of of the body, or of wseckat 
cal agitation by by walking or Tunning, which increase the perspiration, 
suggests itself.” 
