782 
ME. W. K. PAEKEE ON THE STEUCTTTEE AND 
in outline (the broad part below) where they enclose the pituitary fontanelle. They are 
enclosed in a strong ectosteal sheath, the origin of which I showed, in Plate LXXXII. 
fig. 1, as being from the inner layer of the jgarosteal “ rostrum; ” the section is taken 
where the grafting first commenced. The bulbous base of these trabecular roots passes 
directly, behind, into the foremost part of the investing mass, where it encloses the 
posterior fontanelle (Plate LXXXII. fig. 1 ,jp.b.f), and also into the posterior clinoid 
wall (Plate LXXXII. fig. 3 , jj.cl.). This section well shows the absence of all cartilage 
under the pituitary body, and how the “ sella turcica ” is finished below by extraneous 
fibrous bone as in the Osseous Fish. The slice of cartilage seen on each side of the 
trabecular roots (front view) belongs proximally and below to the “ lingulse ” (l.g.), and 
further outwards to the posterior clinoid wall, where it ascends into, and becomes the 
root of, the alisphenoidal lamina (see Plate LXXXIII. figs. 2 & 3, al.s., jp.cl.). There 
is no more cartilage below the thick-edged trabeculae ; the rest of the section is entirely 
formed at the expense of the thick cushion of stroma which intervenes between the 
primordial skull and the faucial skin. 
The broadening end of the “ rostrum ” (“ anterior parasphenoid ”), after forming an 
-ectosteal plate to the roots of the trabeculae and to the “lingulae” (Plate LXXXII. fig. 1, 
b.s., l.g.), performs the same function for the anterior part of the posterior clinoid wall 
(Plate LXXXIY. fig. 1, jp.cl.) ; and this it does until it reaches the lower alisphenoidal 
centre (Plate LXXXIII. fig. 3 ,g>.cl., a.s. 2). Wholly below the cartilage, however, the 
bony matter, which originally commenced in a fibrous tract, breaks away again from the 
primordial skull, and converts large tracts of fibrous tissue into bony wings. Outside 
the bony deposit, shown at fig. 1 , p.cl, the outstretching fibrous bands become bony; 
below the posterior clinoid wall, a strong double pillar of bone growls down from the 
mid line (fig. 1) ; and below, transverse aponeuroses are ossified, so as, with the upper 
wings, to enclose a large space, which becomes the “ anterior tympanic recess ” (a.t.r.). 
Between the lower wings there is a central tract of bone and two open spaces ; and here, 
at every available point, the basitemporals ( b.t .) are forming adhesions with the wings 
that grow out from the basisphenoid (“ posterior pterygoid processes ” of former paper, 
or, more accurately, “ tympanic wings of basisphenoid ”). Laterally the lower basisphe- 
noidal outgrowths have not united with the basitemporals ; thus there is a space ( eu .) 
in which the eustacbian tube is formed. Between the basitemporals there is another 
space ; this becomes the back part of the common vestibule, in which the eustachian 
tubes meet at the mid line. 
The histology of the thick cushion of stroma which intervenes between the primordial 
skull and the so-called mucous membrane of the fauces is peculiar. I have spoken of 
the aponeurotic bands in which the bony matter runs, and must now mention that the 
“ anterior tympanic recess” (a.t.r.) and the eustachian passages (eu.) are, at present, full 
of a delicate gelatino-granular stroma, of a consistence little more dense than the mucous 
tissue of the umbilical cord of the Mammal ; this soft sarcodal substance is soon absorbed 
to form the highly labyrinthic tympanic cavities. 
