148 



THE HUMAN EMBRYO. 



body is straighter, the head is larger, and has risen so as to be about at right 

 angles to the body. The concavity (Nackengrube) below the hind-brain in the 

 outline of the neck is more marked. The limbs are longer, the fingers more 

 distinct. Where the mandibles meet in the median line, the separation of lip 

 and chin has begun. 



Thirty-six Days. Embryos of 14 mm. The correlation of age and size for 



w.b- 



FIG. 87. HUMAN EMBRYO OF ABOUT THIRTY-FIVE DAYS. 



Vit, Yolk-sac. V.S, Vitelline stalk. Am, Amnion. C'/i, Chorion. Vi, Chorionic villi. Al.v, Allantoic 

 vein. Al.a, Allantoic artery. IV. b, Wolffian body, n, Main vein through liver. Lu, Lung. Hy, 

 Hyoid arch. Md, Mandibular arch. MX, Maxillary process. Of, Olfactory pit. (After Coste. ) 



this stage cannot be recorded as absolute, but we may say that embryos of this 

 length are about five weeks old. The body is now nearly straight (Figs. 86 and 

 87). The limbs project beyond the outline of the body in profile views. The 

 ventral outline, owing to the large size of the heart and liver, is very protuberant, 

 and at this stage we find that the portion of the umbilical cord adjoining the em- 

 bryo is greatly enlarged, owing to the distention of its ccelom, so that a large 



