A COMMUNICATION FROM C. DICKENS, M.R.C.Y.S. 127 
By retention or heat, this oxalurate of ammonia becomes 
changed into oxalate of ammonia and urea, and the necessary 
consequence of this would be the deposition of oxalate of 
lime from the calcareous salts of the urine. And if it be 
asked, “ Whence are the nitrogenized matters derived, whose 
metamorphoses give rise to the formation of oxalic acid and 
ammonia ? Are these derived from the tissues of the body, 
like healthy urea and uric acid ? Of course it is quite pos- 
sible that such may be their origin ; but as the quantity of 
oxalate of lime is alwa} T s the greatest after a full meal, and 
often absent in the urina sanguinis , or that passed on rising 
in the morning, and, moreover, disappearing under the in- 
fluence of carefully-regulated diet, and re-appearing on re- 
turning to the use of unwholesome food, it is highly probable 
that the salt is in the majority, if not in all cases, primarily 
derived from the mal-assimilated elements of the food, and 
not, like uric acid generally, a product of metamorphosed 
tissues.” 
Lastly, to mention no more, Liebig maintains that oxalic 
acid is a derivative of uric acid, and not of urea. But as this 
acid is not commonly met with in the urine of the herbivora, 
it being in them the hippuric acid, it seems more probable 
that the view taken by either Dr. Prout or Dr. Bird is the true 
one, and thus the “ fons et origo malorum ” is in the digestive 
organs. 
A COMMUNICATION 
From C. Dickens, M.R.C.Y.S., Kimbolton. 
Sir — The first of January, 1828, produced the first 
number of a periodical devoted to our science. It will not 
become me here to ask, What has it accomplished for us ? 
Sufficient to know that it still exists, having reached its 
twenty-eighth birthday. 
The same month of 1847 announced the loss of one of its 
Editors , the indefatigable Youatt. And now the correspond- 
ing month of 1855 conveys to the profession the mournful 
intelligence of the death of his colleague, the much lamented 
and talented Percivall : a name familiar to u£ as 66 household 
words the name of one who stood first and foremost as 
a veterinary author; whose works, the result of a life of 
industry and observation, may be styled the pupiPs guide, 
