114 GLANDF. 



eight occasions, in the kidneys of dogs. Such motions generally 

 cease, in these animals, in less than an hour after death. . . . 

 I have often seen appearances similar to the preceding, in the kid- 

 neys of the ox and sheep. Nevertheless, it must be stated, that after 

 very numerous and careful observations, I have never seen the epi- 

 thelial cells actually provided with cilia, except upon one occasion, 

 when I observed a single cell apparently fringed with cilia, and in 

 active rotatory motion. This was in the kidney of the ox." . . . 

 " What is observed in the kidneys of the dog, sheep, and ox, cer- 

 tainly seems to be much more powerful than the ciliary motion so 

 readily seen in the oyster *and clam, and very different in its nature 

 from molecular motion. Reasoning from the appearances in the 

 oyster and clam, as well as from analogy in many of the lower 

 animals, it may be concluded that ciliary motion does exist in those 

 of a higher grade, although it is, in them, very imperfect, or, as it 

 might perhaps be said, in a rudimentary condition. In some of the 

 inferior animals, where the urine is excreted in the semi-fluid state, 

 a much greater necessity exists that this fluid should be rapidly pro- 

 pelled in its course through the uriniferous tu^es, and, accordingly, 

 we here find ciliary motion in its most perfect condition. I have 

 never seen it in the human kidney, even after many careful exami- 

 nations. If it does exist, which is probable, it ceases very soon after 

 death, when it rarely happens that we can obtain an opportunity of 

 examining it." Kolliker, in the last edition of his Manual of 

 Human Microscopical Anatomy, Lond. 1860, states (p. 408) that 

 "it (ciliary motion) is absent in birds and mammalia," and yet he 

 has the title of Dr. Isaacs' paper, which was translated into Schmidt's 

 Jahresber. in 185Y, enumerated under the head of literature of the 

 kidney. So that, as far as this distinguished histologist is concerned, 

 Dr. Isaacs' observation of the fact of the existence of ciliary motion 

 in the uriniferous tubes of the kidney in mammalia, is original. 



In regard to the presence of epithelium upon the surface of the 

 Malpighian tufts of the kidney, it is asserted by M. Morel, in the 

 text, that he has seen it on several occasions in the kidneys of the 

 guinea-pig, and also in man. This was originally asserted by Ger- 

 lach, but is doubted by Kolliker (op. cit. p. 408), and denied by 

 Bowman and Dr. G. Johnson (On Diseases of the Kidney, Lond. 

 1852, p. 30, note). The observations of Isaacs upon this point are 



