1888 - 89 .] Dr A. B. Griffiths on the Presence of Uric Acid. 133 
tains is drawn from the surrounding protoplasmic matter, and is 
ultimately forced by the contraction of its walls towards the 
periphery of the hell, and finally ejected into the water in which the 
organism lives its life-history. The contraetile vacuole of Yorticella 
performs the function of a true kidney. Its secretion yields 
microscopic crystals of murexide and uric acid when submitted to 
the same chemico-microscopical reactions as those already described. 
III. Paramcecium. 
Paramoecium loursaria belongs, like Yorticella, to the Infusoria . 
We have in this organism the beginning of a true alimentary canal, 
— with its mouth and slender oesophagus. The contractile vacuoles 
of Paramoecium are situated in the ectosarc almost at each end of 
the long axis of the “body.” These cavities are filled with a trans- 
parent fluid. During the systole fine radiating canals are produced 
which probably communicate with the exterior. 
The contractile vacuoles of Paramoecium loursaria are physio- 
logically the “kidneys.” By the same reactions as those already 
described (in connection with the Amoeba), the secretion of these 
vacuoles yields crystals of murexide and uric acid. There is little 
doubt that these vacuoles get rid of the waste nitrogenous products 
during the systoles which take place periodically. 
In these three primitive forms of the animal kingdom, we have 
the rudiments of a true renal system. The contractile vacuoles per- 
form the same function as the kidney of higher forms, by yielding 
the same nitrogenous substance which is found in the renal organs 
of the highest vertebrates. By the agency of living protoplasm 
(that all-important life substance), even these insignificant micro- 
scopic cells bring about chemical metamorphoses in albuminoid 
molecules, with the production of uric acid and possibly other 
substances. Therefore, in these primitive cells, there lies the same 
power of chemical metamorphosis as we find in the more complex 
cells of the highest vertebrate. 
Through all the multitudinous changes which have taken place 
during the lapse of ages, in the development of the mammalian 
kidney, we find that the physiological functions are the same as 
occur in its original or primitive form (represented by the Protozoa). 
Surely it is not going too far to say that within these lower forms 
