PA NT RE AS OF THE PIG 



231 



15 



Fig. 14 Diagram of 'ui)per bridge' of 80 mm. pig foetus (fig. I) showing he- 

 ginning of formation of structural units as irregularly roundcnl masses; (camera 

 lucida). X 35. 



Fig. 15 Diagram of 'upper bridge' of 110 mm. pig foetus, showing ])rogress 

 in the formation of structural units; i.e., the masses of tissue are larger and 

 more discrete. X 35. 



Fig. 16 Diagram of 'upper bridge' of 140 nun. i)ig foetus, showiiui (dear dif- 

 ferentiation of structural units. At .1 the ducts of one unit have been shown in 

 full; u, unit duct; s, straight duct. X 35. 



