No. I.] THE VERTEBRATE EAR. 75 



has been called Hensen's body or nucleus. Hensen found in 

 the top of the outer hair cells an ovoid refractive body some- 

 what smaller than the nucleus of the cell, variable in size, 

 which seemed to be surrounded by spirally arranged threads, 

 which, notwithstanding its minute size, recalled nerve end 

 bodies and bulbs to our author's mind. Although he usually 

 found it near the upper end of the cell in close relation to the 

 cell caps, he also found it at all distances between the upper end 

 and the nucleus (PL V, Figs. 4, 5, 7, and 8; PL X, Fig. 4; 

 and PL XII). 



This body presented the appearance of a thin walled ovoidal 

 capsule encircled by a fine, evenly, spirally wound fibre. Below 

 this ovoid body, and usually in contact with it, he found still 

 another small round nuclear body, which he thought was, under 

 normal conditions, inside the cell. It is impossible to say what 

 the cause of the peculiar form of the cell's central protoplasmic 

 mass in Hensen's preparations may have been, but I think there 

 is no reasonable doubt that Hensen had under his lens merely 

 a modification of the structure discovered by Boettcher and later 

 observed by Henle, and which I have myself undertaken to 

 describe more fully. The normal condition of this part of the 

 cell, so far as the capillo-nuclear filaments are concerned, is 

 then as follows : The upper end of the cell is filled with a clear 

 protoplasm, more fluid at the circumference and between the 

 threads which lead downwards from the bases of the hairs to 

 the nucleus. These filaments appear to be connected with the 

 nucleus. Whether or not they are so connected is not to be 

 determined readily in the whole cell, but in sections, or, better 

 still, in teased preparations where the parts of the cell are more 

 or less separated from each other. The surface of free nuclei 

 may be seen to be studded with projections, due apparently to 

 the remnants of protoplasmic filaments penetrating the nucleus 

 from the cell protoplasm. In Fig. 8, PL V, is shown such a 

 free nucleus, in which the projections are separated into two 

 sets, each set occupying the polar part of the upper and lower 

 hemispheres of the nucleus respectively. On either side of the 

 nuclear body are two smaller, deeply stained, spherical bodies 

 without visible connection with the nucleus. These two bodies 

 lie opposite each other in the equatorial zone of the nucleus 

 which is free from the projections spoken of above. The struc- 



