EXPLANATION OF THE PLATES. 637 
great plexus (*!) in the cerebellum; h, optic lobe, its 
commissure cut through, both at the front and hind side ; 
h!, optic nerve ; 7, anterior wall of the fourth ventricle 
cut through ; 7’, point where the medulla oblongata sud- 
denly narrows and passes into the spinal tube (/) ; &, cere- 
bellum terminating suddenly behind, against the choroid 
plexus (i!) ; &/’, vascular membrane (pia mater) contin- 
uous from x! over the brain; /, spinal tube; the upper 
half of the tube suddenly thins out (//) as it reaches the 
medulla oblongata; m, the partition between the eyes; 
n, the upper wall of the cranium; n/, the ossified por- 
tion; n/!, ethmoid bone ; 0, muscular layer, which passes 
within and upon the inner surface of the upper wall of 
the cranium; o/, dorsal arch of the first vertebra cut 
through; o!’, dorsal arch of the second vertebra cut 
through ; p, os dentatum, cut through the axis; p/, its 
ligamentous attachment to the base of the skull (r) ; p!’, 
pll', the atlas; p!!’, the upper half of the ring; p!’, the 
lower half; g, second vertebra; r, basal occipital bone ; 
r!, sphenoid bone; 7’, vomer; s, fibrous layer of the 
roof of the mouth; s/, interior portion of s, where it 
hangs down loosely, and is more open, network like ; ¢, 
anterior commissure of the upper jaw, quite hard from 
the considerable amount of ossification ; #/’, termination 
of the horny layer prolonged from the beak (i); u, 
fibro-muscular tongue; w/, commissure of the lower jaw; 
this part is not yet ossified, but the darker part below is 
quite gritty with lime; w!/, opening of the larynx (v) ; 
the darker transverse lines are the tracheal rings; w, 
tongue bone, not yet ossified. 
Fig. 4a; compare wood-cut 4, p. 576. A brain like fig. 4, the 
olfactory and cerebral lobes cut open, and the right pineal 
gland and the right half of the corpora quadrigemina cut 
through more to the right than in fig. 4; 5 diam.; c, tube 
of the olfactory nerve exposed ; d, olfactory lobe with 
very thick walis and a small cavity; e, cavity of the cere- 
bral lobe nearly filled by the choroid plexus; e/, main 
vessel of the choroid plexus where it enters the cavity of 
e; f, pineal gland; g, corpus quadrigeminum of the 
right side cut through, considerably to one side of its 
commissure, to show the very thick upper wall; %!, cho- 
roid plexus of the fourth ventricle partly cut away, to 
show the lamella of which it is composed; //, the upper 
edge of the open medulla oblongata. For the other 
parts compare fig. 4. 
Fig. 5; compare wood-cut 5, p. 576. Transverse section 
through the anterior end of the medulla spinalis, the atlas, 
and a portion of the os dentatum, and also through the pos- 
terior end of the occipital crest; about 15 diam. Corre- 
sponds to the line F, in w-e. 3, p. 576 ; compare also fig. 4: 
a, a’, medulla spinalis; 6, narrow furrow along the upper 
surface of a; c, medullary canal, with a ring of gray 
substance around it; d, pia mater; d!, bloodvessel ; e, 
arachnoid; f, dura mater; g, vessels from the dura ma- 
ter filling the vertebral canal; h, cervical muscles; i, 
processus dentatus, from the second vertebra; 7, the 
canal in the atlas for the passage of i; j, atlas, the dark 
part still soft and gelatinoid, the dead white (k, /) more 
cartilaginous ; /, a small portion of the atlas ossified; m, 
m!, occipital crest; m, the yet cartilaginous part; m’, 
part where a bony deposit has taken place; n, muscle 
running close to, and parallel with, the crest; 0, dorsal 
muscles of the neck; p, musculus intertransversalis; p/, 
musculus retractor capitis. 
Fig. 6; compare wood-cut 6, p. 576. Transverse section 
through the posterior edge of the cerebellum, the choroid 
plexus over the fourth ventricle, the medulla oblon- 
gata and the lower jaw; 5 diam. Corresponds to the 
line E, in w-c. 3, p. 576; compare also fig. 4: a, cere- 
bellum, just in front of its posterior edge; a’, the same 
in the distance, where it descends to join (at a!!) the 
corpora quadrigemina; 6, b!, choroid plexus cut ob- 
liquely to the trend of its oblong mass, showing the 
lamellar structure; ¢, right, and c’, left half of the me- 
dulla oblongata ; c!’, furrow (in ¢, c!) which leads to the 
canal of the spinal tube; c!!’, cavity of the fourth ven- 
tricle; d, pia mater; d/, arachnoid; d!’, dura mater; 
e, vestibule exposed, and here and there cut across; ¢’, 
tympanic cavity; f, still cartilaginous cranium; g, mus- 
cles attached to f; h, fibro-spongiform mesh between g 
and i; i, membrane of the palate; 7, fibro-muscular 
membrane of the floor of the mouth; j, windpipe; 4, 
hyoid bone; /, left branch of the lower jaw; m, blood- 
vessels cut across; 7, muscles; 0, lateral muscles of the 
jaw; p, muscles from the neck; q, deep fold of the skin 
cut across; 7, dense fibrous corium. 
Fig. 7; compare wood-cut 7, p. 577. Transverse section 
through the corpora quadrigemina, the third ventricle, the 
cochlea of the ear, the tympanic cavity, and the lower jaw; 
5 diam. Corresponds to the line D, in w-e. 3, p. 576; 
compare also fig. 4. This view is from the front, look- 
a, the right, and a’, the left half of 
the corpora quadrigemina; 0, the cavity of a, a’, com- 
ing backwards. 
municating through a narrow space (0!) with the fourth 
ventricle, (4'!,) which has its commissure just before this 
point; c¢, the right, and c’, the left fourth ventricle; d, 
inferior commissure of c, c’, a portion of the fourth ven- 
tricle being cut away to expose the origin of the auditory 
nerve, (e/,) which expands (e!) in the cavity of the ves- 
tibule; f, prolongation of the pia mater over the nerve 
