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HUMAN PHYSIOLOGY 



1. 



2. 



FIG. 49. DEVELOPMENT OF THE FCETAL MEMBRANES OF A MAMMAL. 



(After Kolliker.) 



I, ovum with zona pellucida, blastula, and embryonic area; 2, formation of 

 yolk-sac and amnion; 3, union of the folds of the amnion, forming the amniotic 

 cavity; formation of the allantois; 4, decrease of the yolk-sac, increase of the 

 allantois, formation of mouth and anus; 5, reduction of the yolk-sac; allantois 

 joined to the chorion, enlargement of the amniotic cavity; d, zona pellucida; d> ', 

 processes (villi) of zona; sh, serous membrane; sz, villi; ch, chorion, chz, chori- 

 onic villi; am, amnion; ks, head-fold of amnion; ah, amniotic cavity; as, navel- 

 cord with the amnion; aa' ', ectoderm; i, endoderm; mm', mesoderm; dd, embry- 

 onic part of the endoderm; df, area vasculosa; st, sinus terminalis; kh\ cavity of 

 the blastula; ds, umbilical vesicle (yolk-sac); dg, passage of the umbilical vesicle; 

 al, allantois; e, embryo; r, space between chorion and amnion; vl, ventral body 

 wall; hh^ pericardial cavity. 



