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 tine 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 iierve- 

 libres, the thickness of the olfactory epithelium, and 

 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 Kblliker, 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, <fec.) ; 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, 

 : dentical with that of the olfactory region of the nasal 



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