THE MEMBRANA TYMPANI IN THE HUiMAN EAR. 
161 
The cartilaginous ring at the upper part is attached to the malleus, the anterior ex- 
tremity being inserted into the anterior part of the cervix of this bone, and the 
posterior extremity into its posterior part ; the outer surface of this ring has attached 
to it the periosteum, lining the external meatus (fig. 3). If the radiate lamina be 
examined with a magnifying power of ten or twelve diameters, fibres will be ob- 
served whose peripheries are attached to the cartilaginous ring, and their other ex- 
tremities to the malleus. The uppermost of these fibres, however, must be excepted 
from the observation just made, for instead of passing from the superior part of the 
cartilaginous ring to the malleus, they take their course in front of the processus 
brevis and form a distinct layer of membrane covering its outer surface (fig. 3). 
The disposition of this portion of the radiating fibrous lamina is interesting alike to 
the anatomist and to the surgeon, for it is observed to be continuous with the peri- 
osteal lining of the upper part of the external meatus. Mr. Shrapnell, perceiving 
that this portion of the membrana tympani was not so tense as the rest, considered 
it to be a distinct structure, and named it the “ membrana flaccida*.” 
Directly below the processus brevis of the malleus the radiating fibres are attached 
to the ridge occupying the external surface of the bone, but at this part the fibres 
from each half of the membrana tympani are inserted so near to each other that no 
portion of the malleus is visible when viewed exteriorly; towards the inferior extre- 
mity of the long process, however, the fibres are attached to the sides and not to the 
anterior surface, and thus a small portion of the external surface of the long process 
at its inferior part is left bare and is in contact with the epidermoid layer, as may be 
distinctly seen in the healthy living ear by means of the speculum auris and a mag- 
nifying lens. The fibres extending from the malleus and forming the posterior seg- 
ment of the membrane, are one-fourth longer than those forming the anterior seg- 
ment. The thickest part of this layer is that which surrounds the extremity of the 
long process of the malleus, and the most attenuated is that which lies between the 
posterior margin of the long process of the malleus and the circumference of the 
membrana tympani •f-. 
Structure of the Radiate Lamina. 
The fibres composing the radiate lamina, when examined in a fresh state by the 
microscope, are translucent, and with the exception of a few transparent granules, 
present no peculiarity of structure ; the longitudinal parallel wavy lines, characteristic 
of ordinary fibrous membranes, are absent. These fibres are flat, and vary from a 
4000th to a 5000th part of an inch in breadth (fig. 5). In passing from the circular 
* Medical Gazette, vol. x. 
f The blood-vessels ramifying in the upper part of the membranous lining of the external meatus are freely 
continuous with those of the membrana tympani. These blood-vessels are connected by cellular tissue, and 
the two together often form a distinct layer of membrane covering the outer surface of the upper part of the 
external radiate fibrous lamina (fig. 4). See Appendix. 
MDCCCLl. 
Y 
