I. Examining sections through the kidney, hardened in methylated alcohol, of the white mouse, I noticed that the epithelium lining the first portion of the convoluted tubule, i.e. the one following the Malpighian corpuscle, is ciliated, in some instances for a longer, in others for a shorter distance, the cilia being, of course, on the side facing the lumen of the tubule. The epithelium lining the capsule of the Malpighian corpuscle nearest to the neck of the tubule, for about a third or fourth of the circumference of the capsule, is composed of polyhedral or short columnar cells, identical in appearance with those of the convoluted tubule, the remainder of the capsule being lined with flattened squamous cells, commonly found lining the whole capsule of the Malpighian corpuscle in other mammals and man.
In some instances, also these polyhedral or columnar cells of the capsule are possessed of cilia. These cilia are visible only in relatively few convoluted tubules, and, as mentioned above, in portions that are nearest to the Malpighian corpuscles.
The cells to whom these cilia belong show, in some instances, Heidenhain’s rod-like structures in the outer portion of their substance, in other instances they, viz. the rodlike structures, are not well shown, and still in others, they extend more or less distinctly through the whole cell substance.
The cells themselves are polyhedral or short columnar, varying in height, i. e. in the diameter from the lumen to the membrana propria of the tubule, between 0·005 and 0·007 mm.
The cilia are, in most instances, exceedingly fine, and measure in length between 0·0036 and 0·005 mm.
In some places the whole mass of cilia are more or less knitted together, and can be then made out only with high powers as fine striations; in others they appear more isolated, and are then, of course, easiest seen. But in all instances there is a marked boundary line between the cell substance and the cilia, these latter penetrating, however, into the former.
In several instances where the rod-like structures of the cell substance are distinct, I see the cilia directly continuous with them, although, as a rule, the latter are much finer than the former.
Had I found these ciliated cells in an isolated state, i.e. after teasing out little bits of kidney substance, I should have taken them to be identical with the cells figured by Heidenhain (‘Hermann’s Physiologie,’ v, p. 285, fig. 67) of the kidney of the rat, but in our case the cilia are projecting from the cell substance into the lumen of the tubule, the cell substance showing, in addition, the rods of Heidenhain, and there being a definite boundary line between the cilia and the cell substance.
The following are measurements made on tubules lined with ciliated epithelium:
Ciliated epithelium, as far as I can find in the literature of the kidney, has not been seen in the mammal’s organ; in that of reptiles, amphibia, and fishes as is well known (Bowman, Remak, Kölliker, and others), ciliated epithelium is of a constant occurrence in the capsule of the Malpighian corpuscle, and especially in the long thin neck of the urinary tubule; the cilia are here of very great length, and their movement has been observed in the fresh state by Duncan (Sitzungsber. d. Akad. d. Wiss, Wien Abtheil. 56). and Spengel (‘Arbeit, aus d. Zoolog. Instit.,’ Wurzburg, 1876). I have tried to see the movement of the cilia in sections through the fresh kidney of the mouse, but have not hitherto been successful. The sections were made immediately after killing the animal and were examined in aqueous humor, but the urinary tubules of the cortex were always so contracted that of a lumen of the tubules, and consequently of the above-named short and fine cilia, or of the movement of these latter nothing could be seen.
II. Teasing out fresh muscular tissue of the heart of the mouse, isolated fibrillæ of the fibres can be obtained; they (fibrillae) appear of a regular moniliform character, so that they resemble a chain of large micrococci; and indeed I had at first taken them for such, having by accident found them in a drop of blood drawn from the ventricle of the heart by a capillary tube that had been pierced through the wall of the ventricle. On looking, however, through the same blood preparation I met, besides the above isolated ones, two, three, and more such chains joined together sideways, up to whole muscular fibres; so that about their nature, viz. as primitive fibrillæ of muscular fibres, there could be no doubt. Now, the interesting fact that could be made out here was this: passing from a single isolated fibrilla to bits of muscular fibres composed of two, three, and more such fibrillæ, the transverse striation of these several bits of muscular fibres was unmistakably due to the moniliform nature of the fibrillæ, that is to say, corresponding to the varicosities of the fibrillæ were the dark transverse stripes, while corresponding to the parts between the varicosities were the light transverse stripes, or in other words, the dark stripes were made up of the varicosities, the light stripes of the intervening constricted portions of the fibrillæ. This is, I think, a strong corroboration of Dr. Haycraft’s view on the cause of the cross striation in muscular fibres, as described minutely by him in this number of the journal.
