20 



J|*S.'.*^ 



Meseochyme 

 Fig. 4. Photomicrograph of a section through the wall of the umbilical vesicle 

 of the 9.2 mm human embryo, showing cross sections of four large and one small 

 (branch) tubule, and the lining entoderm of the vesicle. The lining cells of the tubules 

 and vesicle are columnar in shape, have a vacuolated cytoplasm and contain the cell 

 inclusions characteristic of this stage. In the older vesicle (of the 13 mm embryo) these 

 mucinous masses and cell inclusions are for the most part lacking and never proximaliy 

 and distally disposed as here. The character of the mesenchyme and the coelomic epi- 

 thelium is also well shown. The mesenchyme contains only blood capillaries. Magnified 

 500 diam. Reduced V3 in reproduction. Made by Dr. LEOPOLD Jaches. 



