86 



GENERAL HISTOHY OF DEVELOPMENT 



(measured from vertex to breech). The chief changes, as far as outward form 

 is concerned, are the formation of the face and external ear, and the development 

 of the limbs. 



FIG. 117. CHOBIONIC VESICLE, EMBBYO, AND YOLK-SAC AT THE BEGINNING OF THE SECOND MONTH. 

 (By permission, from a preparation in the Hunterian Museum, University of Glasgow.) 



Face. In the latter part of the fourth week' the olfactory pits have narrowed 

 down to form grooves running backwards in the roof of the stomodceum. The 



FIG. 118. CHOBIONIC VESICLE, EMBBYO IN ITS AMNION, AND YOLK-SAC TOVVABDS THE END 



OF THE SECOND MONTH. 

 (By permission, from a preparation in the Hunterian Museum, University of Glasgow.) 



margins of these grooves become raised into swellings, which superficially form what 

 are known as the lateral and mesial nasal processes (processus globulares) (figs. 123, 



VUVy 



