126 
CYSTIC CALCULUS IN THE HORSE. 
diately separate it from all its other combinations in the urine, 
forming an oxalate of lime. 
Dr. Prout was of opinion that the source of oxalic acid 
might be traced to the sugar taken in as aliment, and which 
finding its way into the blood, was given off by the kidneys 
when not assimilated. And if we bear in mind the large 
quantity of amylaceous matters the horse feeds on, and which, 
before they are converted into nutriment, have to be changed 
into a saccharine principle, so as to become absorbed, it' is 
not, perhaps, too much to suppose that some derangement of 
the digestive process would be productive of this acid, it being 
remembered that the proximate principles allied to sugar, 
such as starch, gum, and woody fibre, have a tendency, in 
common with it, under the influence of oxidizing agents, to 
undergo conversion into oxalic acid. 
Dr. Golding Bird, however, considers that the existence of 
this acid in the urine is rather owing to an undue quantity of 
urea in this secretion, and that the disease, “ ought to be re- 
garded as a form of azoturia (of which an excess of urea is the 
prevalent indication) in which the vital chemistry of the kidney 
has converted part of the urea, or of the elements which would 
in health have formed this substance, into oxalic acid .’ 5 
He further says, “ the relation between urea and oxalic 
acid is readily shown ; for if we conceive urea to exist in the 
blood, and it be the duty of the kidney to separate it, we 
have only to suppose the organ to exert a slight deoxidating 
or decomposing influence to insure the conversion of urea 
into oxalate of ammonia. We know that, under a depressing 
influence exerted on the nervous system at large, or upon a 
portion of it connected with the functions of the kidney, as 
during typhus, adynamic fever, on the one hand, and blows 
over, or a fracture of, the spine, on the other, such decom- 
posing influence is unquestionable, and the urine becomes 
loaded with carbonate of ammonia, from a re-arrangement of 
the component elements of the urea; one atom of urea and 
two atoms of w ater being resolved into tw o atoms of carbonate 
of ammonia. If, then, a less energetic amount of this mor- 
bidly-depressing influence be supposed to be exerted we shall 
have one atom of urea and two atoms of w r ater lose an atom 
of oxygen to become converted into oxalic acid and ammonia.” 
Some chemico-pathologists have thought that an ammonia 
salt of an acid, called the omluric ,- exists in the urine, formed 
by the elements of urea and oxalic acid. 
lEq. Urea . . C 2 H 4 N 2 0 2 
2 Eq. Oxalic Acid . C 4 0 6 
1 Eq. Oxalurie Acid . C 6 H 4 N a 0 8 
