64 THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 



lary, the rudiment attached to the duct as the dorsal accessory sub- 

 maxillary (Huntington). 



Distad the duct invades a peculiar circumscribed thickening in the 

 mesenchyme (Kolhker, Chievitz), where it divides into branches. 

 In the 14 millimeter embryo there are two primary divisions, a dorsiil 

 and a ventral, the latter continuing the line of the duct (Chievitz). In 

 the 20 millimeter embryo a new group appears from the concavity of 

 the duct (Fig. 5). These three primary divisions are present in the 5 

 centimeter embryo of Bujard, together with an additional ventral 

 duct, which supplies a small lobule, the accessory submaxillar}^ of 

 Bujard, which is probably the equivalent of the ventral accessor}' ele- 

 ment in primates, and at least serially homologous with the recurrent 

 ducts of the supramylohyoid portion of the gland in man, concerning 

 the development of which nothing further is known. 



The definitive orifice of the submaxillary is cranial to the frenulum 

 upon the surface of the phca sublinguahs, that is, lateral to the lingual 

 sulcus. In the 22 millimeter embryo (Fig. 22, p), although it is still 

 a short distance caudal to the frenulum, its position has become parie- 

 tal. The abandonment of the fundus of the sulcus of origin is a fea- 

 ture common to the ducts of the larger saHvary glands. It is most 

 easily accounted for, by the assumption of unequal growth in the walls 

 of the sulcus. The wall in which growth is relatively rapid tends con- 

 stantly to form a new fundus displacing the original one, with the an- 

 lages attached to it, towards the opposite wall, along which they travel 

 upwards as the sulcus deepens. In this case it is the ental wall which 

 appears accelerated, and the argument for an actual roUing outward 

 at the fundus is strengthened by the displacement of the ental parietal 

 flange of the 20 millimeter embryo to an accurately fundal attachment 

 in that of 22 miUimeters (Fig. 22, 11). With regard to the shift craniad 

 of the submaxillary orifice to a prefrenular position, after the abandon- 

 ment of the sulcus, the acquisition of a lumen, and the disappearance 

 of the epithelial crest, our knowledge is very incomplete. Chievitz 

 mentions a small fissure leading craniad from the orifice of the duct in 

 his 10 weeks embrj'o, and states that there is no thickening of the epi- 

 thelium along it. A short proximal segment of the duct in the adult is 

 lined with stratified squamous epitheUum. It is possible that this may 

 have a dift'erent formation from the rest of the duct, as b)- the folding 



