ived from the burning up
of the carbonaceous matter of the feed in the system, one important
factor being the less perfect oxidation of the carbon. Indeed,
Fuestenberg and Schmidt have demonstrated on man, horse, ox, and rabbit
that under the full play of the breathing (oxidizing) forces oxalic
acid, like other organic acids, is resolved into carbonic acid. In
keeping with this is the observation of Lehmann, that in all cases in
which man suffered from interference with the breathing oxalate of lime
appeared in the urine. An excess of oxalate of lime in the urine may,
however, claim a different origin. Uric and hippuric acids are found in
the urine of carnivora and herbivora, respectively, as the result of the
healthy wear (disassimilation) of nitrogenous tissues. If these products
are fully oxidized, however, they are thrown out in the form of the more
soluble urea rather than as these acids. When uric acid out of the body
is treated with peroxid of lead it is resolved into urea, allantoin, and
oxalic acid, and Woehler and Frerrichs found that the administration
of uric acid not only increased the excretion of urea but also of oxalic
acid. It may therefore be inferred that oxalic acid is not produced from
the carbonaceous feed alone but also from the disintegration of the
nitrogenous tissues of the body. An important element of its production
is, however, the imperfect performance of the breathing functions, and
hence it is liable to result from diseases of the chest (heaves, chronic
bronchitis, etc.). This is, above all, liable to prove the case if the
subject is fed to excess on highly carbonaceous feeds (grass and green
feed generally, potatoes, etc.).

Carbonate of magnesia, another almost constant ingredient of the urinary
calculi of the horse, is formed the same way as the carbonate of
lime--from the excess of carbonaceous feed (organic acids) becoming
oxidized into carbon dioxid, which unites with the magnesia derived from
the feed.

The phosphates of lime and magnesia are not abundant in urinary calculi
of the horse, the phosphates being present to excess in the urine in
only two conditions--(a) when the ration is excessive and especially
rich in phosphorus (wheat, bran, beans, peas, vetches, rape cake, oil
cake, cottonseed cake); and (b) when, through the morbid, destructive
changes in the living tissues, and especially of the bones, a great
quantity of phosphorus is given off as a waste product. Under these