39G 



Nose, Pharynx and its Derivatives in Man 



-VP. 



is still connected with the endoderni by a solid stalk (Fig. 3). Directly 

 in front of this angle there is a rounded depression corresponding to 

 the tubercukmi impar. The walls of this depression unite in the middle 

 line and form a ridge running oralwards in the middle line. On either 

 side of this the depressions correspond to the mandibular processes. 



Directly back of the ridges 

 connecting the first visceral 

 pouches there are two deep 

 rounded grooves ; of which the 

 two prominences . of the 3nd 

 visceral pouches form the 

 dorsal boundaries. The model 

 gradually narrows toward the 

 oesophagus, and the two suc- 

 cessive flat ridges, following 

 one another and almost at 

 right angles to the rest, repre- 

 sent the 3rd and 4t]i visceral 

 pouches. The latter pair is 

 not bilaterally symmetrical as 

 the one on tlie riglit side is 

 aboral to the one on the left 

 side. This is not so decided 

 in this embryo as in embryo 

 XII just described. The left is also decidedly larger than the right 

 one, and both show a tendency to become double at their extremities. 

 This does not seem true in the next stage, represented by embryo 

 CLXIII, although it is distinctly true for later stages. The disappear- 

 ance and reappearance of this condition is not understood and in the 

 absence of sufficient material it is suggested that there may be an 

 individual variation in embryo CLXIII. 



In relation to the fate of the 2nd visceral pouch. His first stated that 

 it formed the fossa of Eosenmiiller and the tonsil. This is the descrip- 

 tion that is also given in text-books. Kastschenko ' believes the fossa 

 of Rosenmiiller arises from a furrow between the inner border of the 

 2nd and 3rd arches. His,' in a recent article, agrees that it does not 

 come from the 2nd visceral pouch. 



In the middle line between the prominences of the 4th visceral 

 pouches there is a thin flat projection, the beginning of the larynx. 



Fig. 3. Ventral view of the model of the 

 pharynx of embryo II. Hyp., hypox^hysis ; Oe., 

 oesophagus ; T. i., depression of the tuberculum 

 impar; Thyr. m., median thyroid rudiment; Tr., 

 trachea; V. P.^ V. P/'', V. P/^^ and V. P.>^ 

 first, second, third and fourth visceral pouches. 



'Kastschenko: Das Schicksal der embryonalen Schlundspalten bei Saugethieren. 

 Arch. f. mikros. Anat., Bd 30. 

 ^Loc. cit. 



