1. As varying amounts of calcium oxalate may be held in solution in the urine, conclusions based upon the presence or number of calcium oxalate crystals found therein are of no real value as an indication of the quantity of oxalic acid present.
2. Unless the utmost care is exercised, the results obtained by quantitative estimation of oxalic acid are subject to large percentages of error. This is especially true in the use of Neubauer's or Shultzen's methods, in which the calcium oxalate is precipitated in an alkaline solution.
3. An ordinary mixed diet regularly contains traces of oxalic acid or its salts.
4. A portion of the oxalic acid ingested with the food may be absorbed and reappear unchanged in the urine.
5. The normal daily excretion of oxalic acid in the urine fluctuates with the amount taken in the food, and varies from a few milligrammes to two or three centigrammes, being usually below ten milligrammes.
6. In health, no oxalic acid, or only a trace, is formed in the body, but that present in the urine has been ingested with the food.
7. In certain clinical disturbances which in some of the cases studied above were associated with absence of free hydrochloric acid from the gastric juice, oxalic acid is formed in the organism.
8. This formation in the organism is connected with fermentative activity in the alimentary canal.
(a) The prolonged feeding of dogs with excessive quantities of glucose, together with meat, leads eventually to a state of oxaluria. (6) This experimental oxaluria is associated with a mucous gastritis, and with absence of free hydrochloric acid in the gastric contents.
(c) The oxaluria and the accompanying gastritis are referable to fermentation induced by the excessive feeding with sugar.
(d) The experimental gastritis from fermentation is associated with the formation of oxalic acid in the gastric contents.
9. The symptoms attributed to an oxalic acid diathesis, with the exception of those due to local irritation in the genitourinary tract, do not appear to be due to the presence in the system of soluble oxalates, but are more likely to depend on other products of fermentation and putrefaction.