CHAPTER IV. 



VOMERO-NASAL ORGAN OR ORGAN OF JACOBSON. 



Contents. 1. Vomero-nasal Organ in Man. 2. Com- 

 parative Anatony. 3. Histology. 4. Adjacent Parts. 

 5. Function. 6. Bibliography. 



VOMERO-NASAL Organ in Man. In early infancy all 

 human beings show traces of a pair of organs that are 

 without doubt homologues of the vomero-nasal organs of 

 the lower vertebrates. Each vomero-nasal organ in the 

 new-bora babe is a short tubular structure from a half 

 to two and a half millimeters long and lodged in the lower 

 anterior portion of the nasal septum. The organ opens 

 into the nasal cavity by a minute pore on the free sur- 

 face of the septum not far from its ventral border and 

 onlv a short distance inward from the external naris. 



/ 



The tubular part of the organ extends posteriorly from 

 this minute pore and ends blindly at a point somewhat 

 higher than the level of the pore itself. 



In early human embryos the pore of the vomero-nasal 

 organ can be easily identified on the median face of the 

 nasal chamber just within the anterior naris (Fig. 19). In 

 adults the organ, though commonly present, may disap- 

 pear completely. When present it occurs near the ven- 

 tral margin of the nasal septum (Fig. 20). Kolliker 

 (1877) states that it may vary in length from two to 

 seven millimeters and Anton (1895) gives as the extremes 

 2.2 millimeters and 8.4 millimeters. As seen in trans- 

 verse section it has the appearance of a tube flattened in 

 the plane of the nasal septum. Its lateral wall is cov- 



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