398 



ISTose, Pharynx and its Derivatives in Man 



mentioned only where it is markedly dift'ereut. The same structures 

 are easily recognized here that were prominent in the embryo just 

 described. However, the shape, size and relative proportions have 

 changed markedly. Seen from the side (Fig. -i) another sharp bend 

 has appeared at the oral end in addition to that at the aboral end 

 already noted in embryo II. The part below this ventral (oral) end 

 corresponds more nearly to the adult baccal cavity, especially the roof 

 of it, than any structures that we have yet encountered. Just below 

 this angle the hypophysis joins the mouth. From this angle the 

 model runs dorsally in almost a straight line. This line is broken by 



D.Th.gl 



Fig. 5. Ventral view of the model of the pharynx of embryo CLXIII. D. TL. gl., 

 ductus thyreoglossus; Hyp., hypophysis; Oe., oesophagus; Tr., trachea; V. P.' 

 V. P.'''', V. Y.'" and V. P.'^, lirst, second, third and fourth visceral folds. 



the 1st visceral pouch and the flattened process of the 2nd. Then 

 there is another sharp turn caudalward with a slight dorsal prominence 

 at the angle already mentioned in the description of embryo II. The 

 line then bends slightly ventrally and shows the prominences of the 

 3rd and 4th visceral pouches. 



Seen from above the model is roughly square. The hypophysis being 

 at the ventral angle, the curved dorsal wall of the pharynx at the dorsal 

 end and the two prominences of the 1st pair of visceral pouches at the 

 angles of the square towards the sides of the embryo. Just behind 

 these there is a deep rounded fossa and then a decided process pro- 

 jecting outward and backward, representing the 2nd pair of visceral 



