THE ANATOMY OF TEN TO TWELVE MM. PIG EMBRYOS 



117 



tween, and fused to these thickenings, is the triangular tuberculum impar. The 

 opening of the thyreoglossal duct between the tuberculum impar and the second 

 arch is early obliterated. A median ridge, or copula, between the second arches 

 connects the tuberculum impar with the epiglottis, which seems to develop from 

 the bases of the third and fourth branchial arches. On either side of the sht-hke 



Metencephalon. 



TrJ<! r/inraidcu 

 N< llro/ln'rc'S i>f ni vflcin/c pl/<iloll \ 



Xiuii / 'III 

 \ 

 Toni^iu 



Spinal cord 



Mesencephalon 



Dorsal Pancreas 



Hepatic diverticulum 

 Duodenum 



L. genital fold 



h. mesoHcphros 



Dorsal aorl'l 



phalon 



Post, lobe hypophysis 



Oplii- recess 

 Tclcnrophalon 

 III. lobe hypophysis 



I'lulhus cordis 

 Venlride 

 Yolk ^ac 

 Sepliim transversum 

 ] oik stalk 

 Liver 



Ciecum 



'Small intestine 

 'Allaiilois 

 Urogenital sinus 



Ureter 

 Mesoncphric duct 



Colon 

 U nihil ual arlcry [cut ai^'ay) 



Metanephros Rectum 



Fig. 122. — Median sagittal dissection of a 10 mm. pig embryo, showing the brain, spinal cord and 

 viscera from the right side. X 10.5. 



glottis are the arytenoid folds of the larynx. (For the development of the tongue, 

 see p. 149.) The pharyngeal pouches are now larger than in the 6 mm. pig (Fig. 

 123). The first pouch persists as the auditory tube and middle ear cavity, 

 the closing plate between it and the first branchial cleft forming the tympanic 

 membrane. The second pouch later largely disappears; about it, develops the 



