Om Jacobsonska organets konstruktion och funktion 39 



11) This explains the hitlieito apparently aimless outward and inward move- 

 ments of the tongue of those reptiles. 



12) The organs of Jacobson are probably the most important organ of sense of 

 the snälles. 



13) In those animals (the horse for instance), whose Canalis incisivus is definitely 

 shut off from tlie cavity of the mouth, the organs of Jacobson are to be considered 

 exclusively as setisory organs for scent. 



14) In those animals (for instance the liodents and the Edentata), whose organ 

 of Jacobson opens directly into the cavity of the nose, the chief function of this 

 organ is to act as a sen sorg organ for scent. 



15) In those animals again where the organ of Jacobson opens directly into 

 the bottom of the Canalis incisivus, and in which (as in the ox) the top part of 

 this canal ma}' be shut off from the cavity of the nose by means of pressure with 

 the tongue, the chief function of the organ is undoubtedly to be a smelling organ 

 of the month. 



16) In the Rodents, there is in the anterior part of the hard palate an appa- 

 ratus formed by cartilage and striated musch'-Jihrcs, which opens (respectively shuts) 

 the Canales incisivi, and thereby also the communication between the organs of 

 Jacobson and the cavity of the mouth. 



17) The muscles in question consist of muscular elements migrated from the 

 lips to the hard palate in a late stage of development and these muscular elements 

 maintain continually their connection with the muscles of the lips. 



18) This explains the hitherto apparently aimless and mysterious movements 

 of the snout as in case of the Rodents. 



19) When the orifice of the organ of Jacobson opens directly into the cavity 

 of the nose, the importance of the organ as a sensory organ of scent is hereby 

 probably increased. But this position necessitates a larger quantity of serous fluid 

 in the anterior part of the cavity of the nose. This fact explains the presence of 

 numerous hitherto unhnown glands, which in the Rodents constantly open into the 

 Vestibulum nasi or in the foremost part of tlie Regio respiratoi'ia nasi. 



20) These glands are of importance for the systematic of the Rodents, because 

 they are m«ch alike in closely alHed Rodents, while in less allied they present 

 gradually increased differences, the more distant the relationship is. 



21) If the organ of Jacobson opening into the cavity of the nose, passes 

 through a regressive metamorphosis, the large glands of tlie nose are reduced 

 simultaneously. ^ Such is the case in man. 



22) If the orifice of the organ in the course of development is deplaced to 

 the liottom of the Canalis incisivus, and at the same time there arises a possibility 

 of shutting off the cavity of the nose, while the organ is sucking, then the large 

 glands of the nose will also be superfluous. Their secretion will be compensated 

 by the secretion of the great salivary glands, opening out into the foremost part of 



' Unless their secretion is not wanted for some other purpose. 



