DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 223 



millimeter embryo, as far as the horizontal plane of the furrow (Fig. 

 109, 6). 



In the 70 millimeter embryo and in this alone sprouts occur in the 

 course of the inclusion. These are shown in Fig. 114. One projects 

 ventrad in the cranial fourth of its extent, one dorsad near its termina- 

 tion. Both are caudad of the buccomasseteric nerve and are, there- 

 fore, to be assigned to the pars cyhndrica. They are small, in section 

 circular, and their cells stain very deeply, as is usual in active sprouts. 

 The orbital inclusion thus manifests a tendency to proliferation in the 

 course of the pars cylindrica, as well as in the processus lateralis and 

 perhaps also at its caudal extremity. The reasons for considering the 

 inclusion as the representative of the caudal portion of the maxillo- 

 mandibular plane have already been given. If this view is the correct 

 one, there is no difficulty in interpreting these sprouts as rudimentary 

 glands of the buccal sulcus series. 



The structure of the orbital inclusion resembles closely that of the 

 oral epithelium. At the time of the closure of its fold a single layer 

 of flattened periderm cells with bulging nuclei have appeared. As 

 the fold closes, the periderm layers are brought into apposition. No 

 cleft can be distinguished, as their interlocking nuclei completely 

 conceal the fissure. A firm agglutination of the layers probably does 

 not occur before the separation of the fold, as is shown by the fre- 

 quency before alluded to of small tears through the axial periderm 

 of the fold in embryos otherwise successfully prepared. 



The sections of the separated inclusion show a pale center, which, 

 with sufficient magnification, is found to be composed of clear, faintly 

 stained cells with pyknotic nuclei. The surrounding polygonal ele- 

 ments are arranged in one or two rows, stain deeply, and are precisely 

 like the basal cells of the oral epithelium. The inclusion retains this 

 structure in the 51 milHmeter embryo, where it shows no appreciable 

 increase in diameter, although it has greatly lengthened. In the em- 

 bryo of 70 millimeters the inclusion as a whole is less deeply stained 

 than the oral epithehum, in a considerable part of its length its cells 

 have a turbid look and the nuclei are pale. The central cells in places 

 cannot be made out, and a minute lumen seems to be present. Here 

 for the first time signs of degeneration appear; the buds, however, 

 stain deeply. 



