498 



DEVELOPMENT OF PRIMITIVE BODY FORM 



MAXILLARY PROCESS 



Fig. 244. Development of body form in the pig embryo. (A and B from Keibel: 

 Normentafel zur Entwicklungsgeschichte des Schweines (Sus scrofa domesticus). 1897. 

 Jena, G. Fischer. C, D, and E slightly modified from Keibel, previous reference, and from 

 Minot: A Laboratory Text-book of Embryology. 1903. Philadelphia, P. Blakiston's Son & 

 Co.) (A) About 4 to 5 mm. (B) About 6 mm. (C) Ten mm. (crown-rump meas- 

 urement). (D) Fifteen mm. (E) Twenty mm. 



3. Epidermal Tubulation 



After the neural plate sinks downward and becomes separated from the 

 outside epidermis, the medial growth of the epidermis over the neural plate 

 completes the middorsal area of the primitive epidermal tube (fig. 247E-H). 

 It then comes to enclose the entire complex of growing and elongating neural, 



