PLATE 1 



EXPLANATION OF FIGURE 



1 Photomicrograph of transverse section of umbilical cord of pig. The cord is 

 covered with a stratified epithelium from three to eight (generally four) layers 

 thick, resembling somewhat the transitional type. Tufts of keratized cells 

 occur at certain points (E). To the right of the allantoic duct (All) are the 

 umbilical arteries. The umbilical vein lies below the double remnant of the 

 occluded yolk-stalk (Y.S.). At B.V. is one of the larger arterioles of the ex- 

 tensively vascularized connective tissue. In the area between the lower umbilical 

 artery and the vein, the connective tissue resembles the mucous type; elsewhere 

 it resembles more young mesenchyme, and contains many capillaries, arterioles 

 and venules (A.V.), and also numerous hemoblasts and several typical blood- 

 islands. (Photos, by W. S. Dunn, Cornell University Medical College, N. Y. 

 City. The illustrations were made from the Columbia specimen.) X 18. 



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