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one case, and in the other the influence of the colloidal forms of 
their own substance, from which they are departing in different 
degrees towards crystallinity. 
iii. The large soft spherules, breaking up after a time into 
needles, appear to be magnified spherical molecules. They occur 
under two conditions — in acid urates, of soda and ammonia, and in the 
combinations of hot saturated solutions of urates with chlorides or 
phosphates of alkalies. In both cases they are transitional between 
the gelatinous colloid and the needle. In the second case it is open 
to considerable doubt whether they are merely urates having their 
molecular arrangement altered by the presence of strong saline 
solutions, or whether they are urates in combination with chlorides 
or phosphates. The medium of solution being the same in both 
cases, I incline to the latter view. But this part of the inquiry, 
full of suggestion and analogy, requires a great deal of experimental 
testing. It may be noted that these spheres closely resemble Dr. 
Garrod's drawings of urate of soda from pigeon's urine (Med. 
Chir. Tr., 1848). 
iv. The needle, though a crystalline form, is not by any means 
the true or perfect crystalline form of urate of soda. The true form 
is a short six-sided prism. The needle of urate of soda occurs 
where uric acid would be found in spheres, and urate of ammonia 
in molecules. But it also occurs where uric acid would be in 
crystals — that is to say where no colloid save colloidal modifications 
of itself exists. 
In the cartilage the long, bent, rounded, pointed needle certainly 
recalls the rhombohedron of uric acid in urine, and may be fairly 
supposed to represent some corresponding change to the change 
from flat rectangular plate to rhombohedron with rounded angles. 
But the influence of alkali in altering the behaviour of uric acid 
has yet to be understood. First, what do the Hght spheres of urate 
in strong liq. sodse mean ? Do they mean that a strong solution 
of a crystalloid exerts some of the power of a colloid upon crystalline 
polarity ? Or do they mean that the Hquor sodse, being able in 
excess and with the aid of heat to break up uric acid, exercises 
some of the molecule-disturbing power possessed by colloids beyond 
and above the influence of its density ? Second, why are the needles 
formed in weaker alkaline solutions? Further observation is 
needed to explain this ; but it is not unlikely that these needles are 
also the outcome of transient sphere formations ; and after crystaj- 
lization the alkali may hold the uric acid in a crystalline state. 
V. The bright compact spheres formed by acid urate in gelatin 
approach closely to the urinary forms recorded by several observers. 
They are in appearance like the spheres of crystalloids such as 
carbonate of lime, sulphate of baryta, iodide of mercury, and oxalate 
of copper, all of which when small are bright and homogeneous. 
