MINUTE ANATOMY OF ORGAN OF JACOBSON IN GUINEA-PIG, 227 
great many wavy and more or less convoluted arterial vessels 
connected with one another; in fig. 7 they are seen cut in 
various directions. The capillaries proceeding from these 
arteries are contained in the subepithelial. fibrous layer 
above mentioned, and some of the capillaries enter ‘the in- 
traepithelial spaces described in my first memoir. The 
capillaries lead into the subepithelial venous plexus, and 
smail veins come out from this plexus and pass’ into the 
outer portion of the wall of the naso-lachrymal duct. 
In the embryo guinea-pig that I have examined hitherto, 
at a time when the organ of Jacobson is well developed, also 
the naso-lachrymal ducts are distinctly visible, bearing the 
same position and relation to the surrounding parts as in the 
adult animal. 
An embryo guinea-pig, whose total length from vertex of 
the head to the tail was 4 centimétres, while the long 
diameter of the head, z.e. from the tip of the nose to the 
occiput was 2 centimétres, has been the material from which 
I have made vertical transverse sections through the nasal 
organ. Ina section through the anterior parts, containing 
the Jacobson’s organ as closed tubes, it is noticed that the 
cartilage of Jacobson forms almost a complete capsule round 
the organ of Jacobson, the lateral and median wall of the 
latter being easily distinguishable. Sections made of parts 
a little further back show the cartilage capsule of Jacobson 
open on the upper part, so as to allow the entrance of the 
nervous and vascular branches; the inner or median la- 
mella of the capsule is at the same time much higher than 
the outer one, and in this state the shape of the cartilage 
resembles very much that of the adult rabbit, as I shall 
have soon an opportunity of showing. 
The relations of Jacobson’s cartilage to the nasal septum 
in the front part of the nasal organ and the opening of the 
anterior extremity of the organ of Jacobson into the nasal 
furrow, are exactly the same in this embryo as described 
above of the adult animal. There is, however, this in- 
teresting condition of the lower nasal furrow throughout 
the front part of the nasal organ, viz. that the furrow itself 
is not formed yet, but the stratified epithelium lining 
the median and lateral wall of the septum is fused into 
one solid membrane. But there are smaller or larger 
cavities visible in this membrane; by confluence of these 
along a definite middle plane the furrow becomes gradually 
established. 
The shape and relation of the naso-lachrymal ducts to the 
