468 'Journal of Comparative Neurology and Psychology. 



EXPLANATION OF PLATE V. 



c. capitulum mallei. p:a. processus anterior. 



m. manubrium mallei. /. limbus membrana; tympani. 



p.m. prominentia malleolaris. e.a.m. meatus acusticus externus. 



Fig. I. External surface of right membrana tympani of dog; nerves with their branches only partly 

 shown, n and «', two nerve trunks entering from external auditory meatus over pars flaccid a; (a), 

 branch from manubrium plexus to periphery; (i), branch from limbus towards manubrium. Zeiss 

 comp. oc. 4; obj. 16 mm. 



Fn3. 2. Nerves («) entering at inferior posterior quadrant of right membrana tympani of dog, from 

 external auditory meatus, mm, position of limbus; 2, zonular plexus. Zeiss comp. oc. 4; obj. 8 mm. 



Fiu. 3. Pars flaccida (/»./.) and pars tensa (/). z.) of dog, external surface, after malleus dissected off 

 from within, n, nerves entering from external auditory meatus; ^./). ground plexus; />, plica membranse 

 tympani; c, branching cells in epidermis which readily stain with methylene blue. Zeiss comp. oc. 4; 

 obj. 8 mm. 



Fi<;. 4. Right membrana tympani of cat and adjacent part of middle ear, viewed from within. 

 Through the transparent membrana tympani, nerves («) are seen entering from external auditory 

 meatus all around the periphery, breaking up at limbus (/) into zonular plexus with branches, of which 

 only a few are shown (n.c), to mucous membrane of middle ear and {n.t.) to membrana tympani. With 

 this low power no branch can be distinguished passing from tympanic cavity to membrana tympani. 

 Zeiss oc. 4; obj. 85. 



Fig. 5. External surface of membrana tympani of monkey (Macacus rhesus) after removal of sur- 

 rounding parts, but still adherent to its bony attachments. The manubrium is seen through the mem- 

 brane and the capitulum through the thin bone of external auditory meatus. Nerves («) are seen enter- 

 ing over pars flaccida and posterior plica, and at limbus. a, principal artery to membrana tympani; 

 pp., plica posterior. Zeiss oc; obj. aj. 



Fig. 6. Part of left membrana tympani of monkey (Macacus rhesus), showing nerves entering at 

 upper segment and forming ground plexus {g.p.); a — a' indicate line of principal artery which divides at 

 a' to send branches to each side of manubrium. Zeiss oc. 4; obj. 8 mm. 



Fig. 7. Pars flaccida of dog immediately above plica posterior. Two nerves {n and «') faintly 

 medullated at first which end in interlacing arborizations in fibrous tissue under cuticular epidermis. 

 Zeiss oc. 4; obj. 2 mm. 



Fig. 8. The form of branched-ending seen most commonly under cuticular layer of pars tensa in the 

 monkey. The nerves are nonmedullated. Zeiss, oc. 4; obj. 2 mm. 



Fig. 9. Nerve («) dividing and forming plexus in connective tissue of pars tensa of dog. Zeiss 

 oc. 4; obj. 8 mm. 



Fig. loa and b. Two varieties of nerve endings in fibrous tissue of pars tensa of dog: (a) Nerve 

 («) divides into two branches each of which, after making several corkscrew turns, again divides to sur- 

 round a cell which appears in every respect similar to the neighboring connective tissue cells, (b) 

 Nerve («) gives off branches which coil round each other or the parent stem forming a long narrow end- 

 ing. Zeiss comp. oc. 4; obj. 2 mm. 



Fig. II. Cuticular layer of pars_ tensa of monkey, superior posterior quadrant, (a) Subepithelial 

 plexus with endings in epidermis; (6) Nerve branching and interlacing with subepithelial plexus. 

 Zeiss oc. 4; obj. 2 mm. 



