chap. XLII.] NASAL Mucous MEMBRANE. 337 



canal; it is that part of the gland that is situated 

 in the epithelium of the free surface ; it passes verti- 

 cally through this, and consists of a fine limiting 

 membrane, the continuation of the membrana propria 

 of the gland-tube, and a layer of very flattened epi- 

 thelial cells. 



493. There is a definite relation between the 

 size and number of the bundles of the olfactory nerve- 

 fibres, the thickness of the olfactory epithelium, anil 

 the length of the gland-tubes. The size and number 

 of the bundles of the nerve-fibres are determined 

 by the thickness of the epithelium i.e., by the 

 number of the sensory cells ; the number and thick- 

 ness of the olfactory nerve bundles determine the 

 thickness of the mucous membrane, and the thicker 

 it is, the longer -are the glands of Bowman. 



494. The organ of Jacobson is a minute 

 tubular organ present in all mammals, and, as has 

 been shown by Dursy and Kolliker, also in man. In 

 mammals it is a bilateral tube, compressed from side 

 to side, and situated in the anterior lower part of 

 the nasal septum. Each tube is supported by a 

 hyaline cartilage, in the shape of a more or less 

 plough-shaped capsule the cartilage of Jacobson 

 and opens in front directly into the nasal furrow 

 (guinea-pig, rabbit, rat, &c.) ; or it leads into the canal 

 of Stenson (dog), which passes through the canalis 

 naso-palatinus, and opens immediately behind the 

 incisor teeth on the palate. In all instances, how- 

 ever, it terminates posteriorly with a blind ex- 

 tremity. 



495. The cavity of the tube is lined with stratified 

 columnar epithelium, which on the lateral wall is 

 ciliated in the guinea-pig and dog, and non-ciliated in 

 the rabbit. The median wall i.e., the one next to 

 the middle line is lined with olfactory epithelium, 

 identical with that of the olfactory region of the nasal 



