1922.) ‘ Renal Portal”’ System. 145 
substances. This will be more easily realized when it is 
remembered that high blood pressure, from the standpoint of 
economical excretion, is a most unfavourable condition, since 
it involves an excessive loss of water and salt, which are the 
substances most necessary to be conserved, and a deficient 
elimination of the substances (¢.g. urea) which most require to 
be eliminated (Appendix G, Part III). It is therefore evident 
that it may be necessary for the kidney to possess, on behalf 
of the organism. an automatic mechanism for regulating the 

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other hand, if it be assumed that the capillaries exude lymph into the in- 
tercapillary spaces of the glomerulus and that the inner capsule membrane 
lets the water and salts through while retaining the colloids, it is not easy 
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to the capillaries. The only way out of the difficulty is to assume that 
colloid matter does not leave the capillaries (see footnute 2 on p 59) 
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other words, just as the tissues are relieved from receivin 
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ae of their waste matter (which after all attracts the lymph with food 
and oxygen) but of other substances useful to them by the mediation of 
some other organ. 
