*Previous to entering upon the subject of this paper, it may be permitted me to say a few words respecting the joint labours of Dr. Bright and myself. In the year 1838, having minutely injected a specimen of granular kidney, I perceived that the blood-vessels of the Malpighian tuft were considerably enlarged, and communicated that fact at a meeting of the Westminster Medical Society. Towards the latter end of 1839, I showed Dr. Bright several additional specimens which I had succeeded in preparing in illustration of this view, and received from him a promise of opportunities for further experiment. Accordingly, in the course of 1840, Dr. Bright sent me specimens, accompanied with notes; and during that and the three following years we procured and injected nearly one hundred kidneys, submitting portions of each to microscopic investigation, and carefully noting every matter which seemed of any importance. These preparations are now in my possession. In the year 1841, at Dr. Bright's expense, a series of drawings and engravings was made in illustration of the subject, and of the views to which our investigations had led. Subsequently to this period, various circumstances arose to prevent the issue of a work which had been designed to comprise the results of our joint labours; and I am now indebted to the kind liberality of Dr. Bright for the opportunity of using the illustrations to which I have alluded, and which form a large share of the series accompanying this paper. So sensible, indeed, am I that nearly everything of value which may be contained in the observations which follow, is to be attributed to the assistance of Dr. Bright, that it is not without some degree of diffidence that I venture to prefix my name alone to the present communication.