these changes could be found in the sections of the block taken from the depressed area of the upper pole. " The aetiology of the aneurysm is obscure, but I suggest that it may be the result of a congenital abnormality of the renal artery. The significance of the histological changes in the lower pole of the kidney again is difficult to assess. They do resemble the lesions seen in malignant hypertension and may be regarded as the result of a partial slow ischzmic defect in the upper pole of the kidney resulting from the aneurysm, and in that case probably reflect similar changes in the other kidney." DISCUSSION This appears to constitute a good example of a natural Goldblatt clamp experiment. The pathological changes are characteristic of those produced by experimental renal ischamia. It is interesting to note that though the aneurysm had been present probably throughout life, and certainly long enough to be calcified, the hypertension was apparently of short duration and irreversible changes had not had time to develop in the other kidney.The cause of the ischzmia secondary to the aneurysm remains a matter for speculation. No thrombosis had occurred in the aneurysm, but a calcified plaque had reduced the lumen to a diameter of 2 mm. in one place.It is possible that this reduction in calibre was a recent event responsible for the onset of the hypertension, though an added element of spasm may have been superadded.

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