462 AYERS. 



EXPLANATION OF THE FIGURES. 



Unless otherwise stated, all figures are from preparations of foetuses of Sus scrofa domestica. 



PLATE XX. 



Fig. I. A vertical section of the cochlea of a 14 mm. foetus from the center 

 of that organ. The course of the fibres in the modiolus is well shown. The 

 characteristic shrinkage in the size of the nerve-bundle after leaving the ganglion 

 is given, and the appearance of the ganglion in cross-section as stained with the 

 silver method is that commonly found in these preparations, but does by no 

 means convey a truthful idea of natural conditions. At a, one hair-cell, two 

 supporting cells, and some of the nerve branchings in the Sauropsid organ are 

 shown ; b shows the branching nerve better, while c does the same for the sup- 

 porting cells ; in d and e the Cortian organ and the nerves running to it are 

 shown ; non-nervous parts in outline. Htnk. obj. ^ of 2 Obh. camera. 



Fig. 2. A single cochlear canal and its ganglion and nerves from a section 

 similar to the above, more highly magnified. At //, three outer hair-cells and 

 their relations to the nerve fibres indicated. The continuity of one nerve fibre 

 and hair-cell is shown. 



Fig. 3. Surface view of a portion of the Sauropsid organ showing the con- 

 tinuity of the nerve fibre and sensory cells. 



Fig. 4. A portion of the nerves included between the cochlear ganglion and 

 the outer hair-cells. With this magnification the connections of the radial nerves 

 with the spiral bundle are not clearly defined. In the region of the lamina the 

 aberrent fibres do not occur in bundles. Three ganglion cells and numerous 

 sheath cells occurring as varicosities are shown. Htnk. obj. 2 Obh. cam. 



Fig. 5. A portion of the arch of Corti with five inner hair-cells with their 

 nerves. The elements of Corti's arch are stained a rusty brown, while cells and 

 nerves are completely black. Htnk. obj. 5 Obh. cam. 



Fig. 6. Six ganglion cells from the cochlear ganglion. These are all multipolar 

 cells save one " X ," which is a double ganglion cell. Htnk. obj. 5 Obh. cam. 



Fig. 7. About one quarter of a complete turn of the cochlear lamina, showing 

 the appearance and relations of the constituent parts of the nerve plate of the 

 lamina. Near the ganglion one notices suboval spaces free from nerves ; these 

 spaces later on are occupied by bone. The nerve fibres run both ways from the 

 ganglion. The spiral bundles of fibres appear as complete with this power. , A 

 few hair-cells are sketched in, but only such detail is put down as could be intro- 

 duced into a drawing on this scale. Htnk. obj. 2 Obh. cam. 



