5d-4 DR, E. KLEIN. 
deficiency affecting the lower and outer wall, the plough-shaped 
upper wall (see fig. 2, Pl. VII, in this year’s January number of 
this Journal) being the last part of Jacobson’s cartilage to dis- 
appear. In the rabbit, on the other hand, it is the outer and 
upper part of the capsule which becomes wanting, so that Jacob- 
son’s cartilage represents a hook-shaped or trough-shaped organ, 
the opening being in the upper part of the wall. 
As regards the presence of an inner and outer Jabium, and as 
regards the elongation of the former as we pass backwards, there 
is nothing of the kind in the guinea-pig. The cartilage of Jacob- 
son agrees in its general shape, 7.e. being a trough-shaped plate 
with its opening directed upwards, more with the ideal cartilage of 
Jacobson described by Gratiolet! of the mammal, and to some 
limited extent also with that of the sheep, mentioned by Balogh,’ 
and figured by him in figs. 15, 16, and 17 of his plate iv, being 
here represented in some places as a trough-shaped capsule with 
an upper opening. 
Another point of dissemblance between the cartilage of Jacobson 
in the rabbit and guinea-pig is its relation to the upper maxil- 
lary bone. 
As I have shown in figs. 4, 5, and 6 of Plates XVI and XVII 
in the April number, 1881, of this Journal, the cartilage of 
Jacobson in the guinea-pig 1s supported already in the most 
anterior part of the organ of Jacobson, and even at the mouth 
of this latter, by a lamina of osseous substance extending on each 
side from the superior maxilla on the inner or median surface of 
Jacobson’s cartilage. This bone is in reality the front part of 
the crista nasalis of the superior maxilla. When Jacobson’s 
cartilage has assumed the shape of a more or less perfect 
capsule, the bone forms an almost complete capsule around 
Jacobson’s cartilage, as is shown in figs. 1 and 2 of Plate VII 
in this year’s January number of this Journal. In the pos- 
terior portion of the organ of Jacobson the cartilage of Jacobson, 
as mentioned previously, disappears altogether, and now the 
organ of Jacobson is altogether surrounded by the bone of 
the crista nasalis of the superior maxilla. Thus it is in the 
guinea-pig; in the rabbit the relations are altogether of a differ- 
ent nature, as is shown in figs 4 to 8. 
In the rabbit Sacobson’s cartilage is supported on its lower 
wall by the intermaxillary bones separated in the median line by 
their respective inner periosteum. ‘This relation is noticed already 
before any trace of the organ of Jacobson is reached, and it remains 
the same past the region in which Jacobson’s cartilage has assumed 
the shape of a complete capsule (see fig. 4). Soon after this 
Vine, p. ZL. 
7 L.c., p. 451. 
