MINUTE ANATOMY OF ORGAN OF JACOBSON IN GUINEA-PIG, 221] 
lage of the concha reduced considerably in extent, being now 
for the greater part replaced by bone, with the exception of 
an oblong angular piece, which extends above the naso- 
lachrymal duct (see below). 
In the sections still further behind that of which fig. 3 is 
a representation the individuality of the above curved carti- 
lage plate is well seen. Its shape and relation to the septum 
are now different from that before mentioned, as is easily 
understood from a reference to this fig. 3, and it is, therefore, 
unnecessary to enter into any lengthy description. ‘This curved 
cartilage plate is the front end of the cartilage surrounding 
the Jacobson’s organ, 27.e. the Jacobson’s cartilage, and as 
such is referred to in the figures at 8. While in the parts 
delineated in figs. 1, 2, and 3 the concave surface of Jacob- 
son’s cartilage is directed upwards, forming, at the same 
time, the bottom of the lower nasal furrow (see the figures), 
in the parts further backwards, such as are shown in figs. 4 
and 5, the cartilage becomes so changed that its concave 
surface is directed outwards, while its convex surface is in 
close contact. with the lower margin of the cartilage of the 
septum, but separated from this latter by the respective peri- 
chondrium and a small amount of loose connective tissue 
with fat cells (see the figures). 
As is also well shown in the drawings, the two extremi- 
ties of Jacobson’s cartilage, especially the upper one, become 
very bulky as we pass further backwards; (see fig. 6). Still 
more backwards the Jacobson’s cartilage assumes the shape 
of a more or less complete capsule around the organ of 
Jacobson on each side, such as I have described and figured 
in my previous memoir, and for thisreason I need not further 
enter into this subject. 
Towards the posterior extremity of Jacobson’s organ the 
cartilage so alters that the lower part gradually altogether 
ceases, and only the upper plough-shaped portion (see fig. 2 
in my former memoir) remains; its channels, including the 
large afferent branches of the vessels and nerves of the organ 
otf Jacobson become gradually enlarged, and finally all traces 
of the cartilage are lost. But this total disappearance of the 
cartilage of Jacobson occurs long before the hind or cecal 
extremity of the organ of Jacobson is reached, its place 
being taken by the bone of the nasal crista ; see figs. 7. 
Another point to be noticed in figs. 4,6, and 7 of the 
present memoir is the relation of the upper maxilla, or, more 
correctly speaking, of the nasal crista, to the Jacobson’s 
cartilage. Beginning with a part illustrated in fig. 4 we see 
at 11 the first indication of the nasal crista of the upper 
