140 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



is a deep pentagonal cavity. Its lower boundary is 

 formed by the mandibular arch, while laterally are 

 to be found the maxillary processes of each side. 

 Its upper boundary is formed by an unpaired growth 

 called the nasofrontal or nasal process (Fig. 100.) 

 Situated on each side of the nasal process are the 

 nasal pits. Each pit divides the nasofrontal process 

 into a lateral external portion called the lateral 

 frontal protuberance , which forms the outer boundary 



Ventricle of cerebrum. 



Place from which the hy- 

 pophysis is developed. 



Stomodeum. 



Heart. 

 Pore gut. 

 Notochord. 



Third ventricle. 



Fourth ventricle. 



Spinal cord. 



Fig. 10 1. Median section through the head of an embryo rabbit 

 6 mm. long (after Mihalkovics) 



of each nasal pit, and a median or central portion 

 called the globular protuberance, which constitutes 

 the inner boundary of each pit. The two lateral or 

 side protuberances grow around the olfactory pits 

 and form the alse of the nose, while the two central 

 portions develop into the intermaxillary bone con- 

 taining the incisor teeth and the center of the lip. 

 By studying the text figures a correct idea of these 



