402 THE NASAL REGION IN EUTAENIA. 
slight prolongation forward is found (c), aud which appears in sec. 
tion in Fig. 4. A similar prolongation is found on the level of the 
turbinal, the cartilage of which furnishes a ledge on which the duct 
rests fora short distance, after which it is completely surrounded 
by the lachrymal bone for a portion of its course. As it approaches 
the eyeball it lowers to its anterior angle, and takes a sharp turn 
inward and upward to terminate in its gland, situated on the inner 
‘surface of the eyeball, and separated from its fellow of the opposite 
side by the basisphenoidal rostrum. 
The cartilages (Figs. 3, 4, /c’, Zc”) which have been termed lachrymal 
above, are but backward continuations of the transverse band con- 
necting the turbinal cartilage with that of the pedicle ot the Organ of 
Jacobson. When the lachrymal duct has reached the palatine bone, 
they apply themselves to its outer and under wall and fuse, forming 
a plate continued behind with the blindly ending basal portion of the 
duct. The plate behind the latter becomes flattened horizontally, and 
terminates in front of the choana of its side. 
The sections from the embryo head reveal some important points 
which may be summarized here. 
The roof of the mouth exhibits in the main the features of the 
adult palate. No glandular structures are present, there being but 
an involution of the lining membrane to form the future upper lip 
gland. (Fig. 5, g/.) The opening of the Organ of Jacobson is situated 
in the groove to be found laterally from the choanal depression. 
The Organ of Jacobson has the same form as in the adult. The 
cellular columns number about twenty in each section, while in the 
adult the number reaches sometimes as high as sixty. But the 
remainder of the roof, of which they are the constricted portions, is 
much thicker, and in it 8-10 layers of cells may be counted. Neither 
these nor those of the columns are possessed of peripheral processes, 
at least such are not demonstrable. Fibres arising from the inner 
surfaces of the olfactory lobes pass down the sides of the septum, 
enter the outer ends of the columns, and terminate at its cells. The 
whole roof does not exhibit, in addition to the division into columns, 
any difference from that lining the upper nasal chamber. Its floor 
is lined by two layers of interfitting columnar cells. 
The continuity of the cartilage of the Organ of Jacobson with that 
of the nasal cavity, which only a study of many sections of the adult 
shows, is demonstrated by one, or at most two sections, from the 
