= 
0 
1922.] ‘* Renal Portal ’’ System. 149 
Personally I do not accept the pump theory for reasons already 
Stated (absence of suitable pulsation, no necessity, no evidence 
for intracapsular space). 
The third and last explanation of the Encapsulation of the 
glomeruli is based upon the fact thatall organs developed at the 
sides of the vertebral column, between this, the stout peritoneum 
and the powerful myotomes, are subjected to considerable cons- 
tant and intermittent pressures, due both to the small amount 
of available space and to the contractions of the myotomes in- 
Volvedin locomotion. It is to escape these pressures, or at least 



Pa: hout interfering with p in the other parts of the kidney. If 
the space between the inner and outer capsule walls of each glomerulus 
Were & vacuum, then at each contraction of the 2,000,000 odd glomeruli of 
the human kidney, e.g. 2,000,000 capsules would contract, and this change 
apsules co i i nsid 

to and fro movement of a amount of urine, the cap remaining 
constant in size, the perturbations referred to would be avoided 
ne 
the capsules (34). In Amphioxus the 
erulus is represented by a small reticulation of the artery lying above 
and not in contact with the nephridium. 
