352 



HUMAN UTERUS AND FCETAL APPENDAGES. 



that the coelom is entirely obliterated, that the yolk-stalk has usually been com- 

 pletely resorbed, and that only traces of the allantois can be seen, Y. The blood- 

 vessels have grown; there are two arteries, A, A' , and a single vein, V. Around 



A' 



FIG. 211. CROSS-SECTION OF A HUMAN UMBILICAL 



CORD AT TERM. 



A, A f , Umbilical arteries much contracted. V, Um- 

 bilical vein. Y, Remnant of allantois. X I2 diams. 



FIG. 212. SECTION OF THE ALLANTOIS FROM A 



HUMAN UMBILICAL CORD OF THREE MONTHS. 



ent, Allantoic entoderm. mes, Mesoderm. X 34 



dianis. 



FIG. 213. CONNECTIVE TISSUE FROM THE UMBILICAL CORD OF A HUMAN EMBRYO OF 21 MM. STAINED 



WITH ALUM COCHINEAL AND EOSIN. X 54 diams. 



n, Nucleus, p, Protoplasmic network. 



