74 



FREDERICK TILNEY AND LUTHER F. WARREN 



of the later st :!<:<> in the cat is shown in figure 42, illustrating the 

 conditions in a 70 nun. embryo. Models by one of the authors 

 show the existence' of this twofold structure in the cat as late as 

 120 nun. embryo. 



7 



25 



35 



Kig. 40 Mesial view of forchrain reconstruction of 30 nun. cat embryo. X 50. 

 The unshaded area shows the cut surfaces of the reconstruction, according to 

 Tilney, 1915 



2, chiasmat ic process; I, chiasm; 5, corpus interpedunculare; 7, epiphysis; 9, 

 foramen of Moiiro; 1 1 . infundibular stem ; 12, infundibular canal ; lo, infundibular 

 process; '_'(), lamina terminalis; 25, mammillary region; 32, post-chiasmat ic emi- 

 nence; 33, post-chiasmatic recess; 34, post-infundibular eminence; 35, post-in- 

 fumlibular recess; 39, dorsal sac ; 40. recess of t he infundibular process; 41 supra- 

 optic crest ; }2. supra-optic recess. 



The most recent study of the pineal region in mammals is that 

 of John Warren, 117 in which he brings to a conclusion his excel- 

 lent series of papers upon the interpretation of this region of 

 the brain in vertebrates. Of the human embryo he gives the 

 following description (fig. 43): 



