DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 



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lection of one or other of these lines, following either the parotid duct 

 along its mesal surface or else, directed caudad close to the oral epi- 

 thelium, seek the orbital path. A very few, to be considered in detail, 

 seem to vacillate between these alternatives. A large majority follow 

 the parotid, as the orbital path appears to be unfavorable on account 

 of its contracted limits and the long distance that must be traversed, 

 before room for e.xpansion can be found. As regards the attachment 

 of the sprout there are three possible sites: viz. the angle between the 

 parotid and the oral epithelium, the parotid duct, the oral epithelium 

 itself. The element in a few cases loses its connection altogether and 

 is found embedded in the mesenchyme as an orbitoparotid inclusion. 



In 6q embryos between 12.5 and 70 millimeters, counting each side 

 separately, the orbitoparotid element was found 49 times, as follows : 



From the angle between the parotid and the buccal sulcus, 13. 



From the parotid duct, 5. 



From the buccal sulcus, 26. 



As an inclusion, 5. 



In the younger embryos the sprout is regularly at the angle between 

 the parotid and the oral epithelium, springing from the intermediate 

 portion of the ])arotid flange. After 14 millimeters this condition is 

 rare. Its latest occurrence is at 19 milUmeters. When we consider 

 that the parotid attachment advances craniad, and that the duct is 

 freed by a reduction of the intermediate portion of the flange, it is 

 evident that a sprout cannot long retain this position, but must either 

 be carried laterad with the duct or left behind as the parotid advances 

 if it retains its connection with the buccal sulcus. In its earlier stages 

 the orbitoparotid is simply a thickening of the intermediate portion 

 of the flange, not yet extending free into the mesenchyme, as, for ex- 

 ample, in the 13.5 millimeter embryo (Figs. 34, 40). In slightly older 

 embryos it forms a minute projection caudad for a section or two, as in 

 the 15 miUimeter embryo of Fig. 45. In embryo No. 127 (Fig. 43) 

 may be seen the mode in which this position is lost. The orbito- 

 parotid bridge is interrupted by a narrow oblique incisure close to the 

 parotid, leaving a shghtly thickened portion of the flange attached to 

 the parotid. In the fragment remaining attached to the sulcus we 

 have the possibility of a second sprout, realized only once in our series 

 in embryo No. 249 of 18.5 millimeters (Fig. 99). Of the two cases of 



