150 



THE DISSECTION OF PIG EMBRYOS FOR STUDY 



diencephalon appears the anlage of the epiphysis or pineal gland, and the chorioid 

 plexus of the third ventricle. This extends into the lateral ventricles as the 

 lateral chorioid plexus. The dorso-lateral wall of the diencephalon thickens to 



Isthmus 

 Metencephalon 



Mesencephalon 



Chorioid plexus fourth ventricle 

 Hypophysis 



Tela chorioidea fourth ventricle 

 Myelencephalon 



Epiglottis 



Notochord 



Esophagus 



Trunk pulm. artery 



Wall of atrium 



Foramen ovale 



Trachea 



Lung 



Dorsal aorta 



Stomach 



Intersegmental 

 arteries 



Pancreas 



Common bile duc\ 



Duodenum 



Third ventricle 



Diencephalon 



Corpus striatum 



Cerebrum 



Genital ridge 



Metanephr'os 



Mesonephric duct 



Semilunar valves 

 R. ventricle 

 Yolk-sac 

 Diaphragm 

 Yolk-stalk 

 Liver 

 Caecum 

 Colon 



'Small intestine 

 ~Allantois 

 Bladder 

 Phallus 



Urogenital sinus 

 Rectum 



Ureter 



FIG. 141. Median sagittal dissection of an 18 mm. pig embryo, showing central nervous system in 



section and the viscera in position. 







form the thalamus and the third ventricle is narrowed to a vertical slit. The 

 increased size of the cerebellum has been noted. Into the thin dorsal wall of the 

 myelencephalon grows the network of vessels which form the chorioid plexus of 



