THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 41 



14. Chievitz. Embryo of 12 weeks. The parotid has attained 

 essentially its definitive form and position. 



15. Chievitz. Second embryo of 12 weeks. A furrow running 

 entad from the angulus oris terminates without reaching the parotid 

 orifice, which has ceased to be sulcal in position. It is situated i.io 

 millimeters behind the angulus oris. With regard to the duct Chie- 

 vitz writes : — 



Es fand sich an demselben Embryo ein merkwurdiger Seitenast dcs Ductus 

 Stenon., welcher citien ahnlichen X'crlauf hat, wie der beim zehnwochentlichen 

 Embryo erwiihnte Gang. Kurz vor dcm vorderen Randc des Masseter geht 

 von der medialen Seite des Ductus parotideus ein nach hinten gerichteter Gang 

 ab, welcher medial vom Masseter sich bis zum Ptervgoidcus int. fortselzt und nach 

 einem Veriauf von i millimeter blind endet. Der auf dem Querschnitte runde 

 Gang sieht aus ganz wie die iibrigen Driisengiinge; er besitzt in seinem grosseren 

 Theile em Lumen, umgeben von Epithelzellen, deren Langliche Kerne in zwei 

 Reihen geordnet sind. Der N. buccinatorius kommt von hinten her zwischen dem 

 M. temporalis und M. pterygoid, int. auf den Gang herab und schlagt sich um die 

 laterale .Seite desselben, um ihn weitherhin an der unteren Seite zu begleiten. Ein 

 Blutegefass liegt lateral vom Nerven. 



Recently Elizabeth Weishaupt has published a study of the orbital 

 inclusion which she interprets as a rudimentary branch of the parotid 

 (ramus mandibularis ductus parotidei). She notes the condition of the 

 parotid anlage in four embryos, one of 13.5, two of 18, and one of 25 

 millimeters. It is at first a slight thickening in the course of the buc- 

 cal sulcus. Later it is displaced to a dorsal parietal position. The 

 solid duct is freed by constriction and secondarily acquires a lumen. 

 In all of these embryos she failed to find the orbital inclusion, or, to be 

 precise, found no branch associated with the parotid anlage. In seven- 

 teen other embryos ranging from 17 millimeters to 40 millimeters in 

 length an epithelial cord or duct was uniformly present between the 

 buccal sulcus mesad and the masseter and internal pterygoid muscles 

 laterad, and in close relation to the buccal nerve. In three fetuses of 

 7.5, 10, and II centimeters the structure was also found, and while 

 reduced in length, yet showed a tendency to further development in 

 the formation of sprouts, a most important observation, which goes 

 far to place the orbital inclusion in the class of ductless glands. In 

 none of these embryos was the inclusion connected with the parotid 

 duct. 



The foregoing data suffice to show that the buccal sulcus in 



