Mervin T. Siidler 



397 



In this embryo the mouth is a transverse slit with only the hypophysis 

 to break the lines. In none of my models does it appear as a five-sided 

 object usually described since His first mentioned it as such in human 

 embryos of the 3rd week. Hammar " also disagrees with His and finds 

 it alwavs as a transverse slit. 



A 



I Thyr.m. ^ ^ 



Hp 



'"■■M:„ 



"'',:,J'"""" 



Fig. 4. Lateral view of the model of the pharynx of embryo CLXIII. Magnified 

 15 diameters. Hyp., hypophysis; N., outline of the side of the nasal depression; 

 Oe., oesophagus; Thyr. m., median thyroid rudiment; Tr., trachea; V. P.^, V.P.^'', 

 V. V/^^ and V. P.'^, first, secoij^, third and fourth visceral pouches; A. B., line of 

 section seen, Fig. 6. 



Emhri/0 CLXIII. 



This embryo has a vertex-breach of 9 mm. and a neck-breach 9 mm. in 

 length. It is about 30 days old or an embryo of the early 5th week of 

 development. Two models were made of the pharyngeal cavity of this 

 embryo. The first represents the cavity simply, while the second one 

 includes also the mucous membranes lining it. The description will 

 apply to the model of the cavity alone and the second model will be 



'Aug. Hammar: Notiz iiber die Entwickhmg der Zunge und Mundspeicheldriisen 

 beim Menschen. Anat. Anz., Bd. XIX, 1901. 



