THE NASAL REGION IN EUTAENIA. 397 



nuclei, but after a stay in Miiller's Fluid the nucleus is found adjacent 

 to the wall of the now perfectly spherical cell. The opening of the 

 gland takes place at an indentation on the surface of the membrane. 

 The following account of the structure of the Organ of Jacobson 

 based partly on my preparations, was contributed by Prof. Wright 

 to the Zoologischer Anzeiger (No. 144), and will serve to explain his 

 figures (Nos. 8, 9, 10) : 



"The Roof. — Immediately within the osseous capsule which the 

 Vomer forms for Jacobson's Organ lies a somewhat scanty mucosa 

 which is largely occupied by olfactory nerve-bundles : it is more 

 richly pigmented than the corresponding layer in the nasal cavity, its 

 blood-vessels are of larger calibre, and it is destitute of Bowman's 

 Glands. Most of the elements of the mucosa are continued inwards 

 towards the lumen of Jacobson's Organ between its cellular columns 

 which are thus isolated from each other by pigmentary connective- 

 tissue and capillary vessels. Very few of the olfactory nerve-fibres 

 appear to run in the partitions thus formed, the bundles entering the 

 outer ends of the cellular columns almost entirely. The capillaries 

 arrived at the deep surface of the Neuro-epithelium form there a 

 plexus, the polygonal meshes of which are occupied by the inner 

 ends of the cellular columns. This plexus obviously corresponds to 

 that on which the Neuro-epithelium in the nasal cavity rests ; but 

 there, is no intervening basement membrane, for a reason which will 

 be presently apparent. The Neuro-epithelium- (inside the plexus) is 

 only 33 ft high, and the greater part of this belongs to the superficial 

 stratum (as defined above), while only one or two layers of cells cor- 

 responding to the nuclear are to be detected. These latter cells, 

 however, differ in form, according as they stand opposite a node or a. 

 mesh in the capillary plexus ; in the former case they are shorter 

 and their deep processes are bent in such a manner as to pass around 

 the vessel, in the latter case they are more fusiform and they retain 

 this shape for three or four layers while passing through the mesh 

 in the corresponding cellular column. With the exception of these 

 spindle-shaped cells which form their inner ends, the cellular columns 

 are formed entirely of cells, completely resembling those of the nu- 

 clear stratum in olfactory epithelium of the nasal cavity ; i. e., they 

 possess rounded nuclei (6 — 7 fi X 5 f 1 ) surrounded with very scanty 

 protoplasm prolonged into processes at either end. The highest, 

 columns measure about 300 fi. 



The Floor. — The following structures v may be traced from roof to 

 floor. 



(1) The layer of ordinary cylindrical epithelium cells which are 

 now only 15 /* high and bear short cilia ; between the bases of these 

 are wedged small rounded cells forming rarely more than one layer ; 

 these rest on 



