From these records it would seem that renal and pelvic calculi occur almost exclusively in herbivorous animals. At least true stones forming in the renal pyramid and pelvis are found most characteristically developed in the Ungulata, the typically herbivorous mammal. Judging by the bilateral distribution of stones and uratic collections, local processes, inflammation especially, have less to do with their production than the availability of precipitable inorganic salts in the urine. TUMORS. Tumors of the kidney have been observed sixteen times, fourteen of which were primary and two secondary. The latter two concerned an epitheliomatous metastasis from a malignant papilloma in the stomach of a Kangaroo (_Macropus rufus_) and a sarcoma growing like an infarct secondary to a mediastinal tumor in a Dorcas Goat (_Capra hircus_). The only important primary tumor of the kidney in a mammal was found in a Gray Squirrel (_Sciurus carolinensis pennsylvanicus_), a solid gray nodule composed histologically of large and small deeply staining cells, many containing large vacuoles and fitted with a small dark nucleus. The arrangement of the elements was in irregular acini or bundles and thereby suggested the tumor known as hypernephroma. A small nodular adenoma was found at the upper end of the right kidney in a common opossum (_Didelphys virginiana_) and seemed to be purely of renal construction in that an attempt to retain tubular arrangement was evident. [Illustration: FIG. 21.—CALCULI FROM RENAL PELVIS TO END OF URETHRA. COMMON RACCOON (PROCYON LOTOR). THESE STONES WERE PALE YELLOW-GRAY. THEY CONSISTED OF A URATIC BASE, BUT SOME PHOSPHATES AND CARBONATES WERE FOUND. THE RIGHT KIDNEY WAS NOT AFFECTED. THERE WAS ONE IRREGULAR CALCULUS AND THIRTY-SEVEN SMOOTH MASSES FROM BLADDER TO END OF PENIS. THIS CASE IS NOT INCLUDED IN STATISTICS. OCCURRING AFTER THEIR COLLECTION HAD CEASED. ]