On the morphology of the renal tubules of vertebrates

A comparative study of the renal tubules of the different classes of vertebrates was projected nearly twenty years ago, soon after publishing results of a study on the development and shape of the uriniferous tubules of the higher mammah.1 In this study, as projected, it was purposed to reconstruct the excretory tubules of the pronephros and mesonephros of certain of the lower vertebrates, including amphibia, and the metanephric tubules of certain reptiles, birds and mammalia. In the reconstruction, by the Born wax plate method, of the pronephric tubules of a larval toad, and mesonephric tubules of an adult frog and the metanephric tubules of certain reptilia no great difficulty was experienced, and such reconstructions were made, somewhat over fifteen years ago in conjunction with Professor Ward J. MacNeal, sometime Instructor in this department. On attempting to reconstruct the metanephric tubules of birds, it was learned after unsuccessful trials that this was beyond the limits of the method, so also with endeavors to reconstruct the metanephric tubules of adult mammalia. The projected study, therefore, was abandoned for a time. The form of the adult, mammalian renal tubule was later ascertained by specially devised methods of teasing.? This special method of teasing has relatively recently been successfully used in an investigation of the form of the metanephric tubule of birds. I am in a position now, therefore, to present figures giving the morphology