xxii LIST OF ILLXJSTEATIONS. 



cord of a human embryo at the beginning of the fourth week. 

 (After His) ^22 



226. A diagrammatic transverse section across the spinal cord of a human 



embryo of the fourth week. (After His) 525 



227. A diagrammatic figure of a human embryo lettered by Professor 



His, K.0, and estimated as thirty-one days old. The figure shows 

 the brain and spinal cord, and the cranial and spinal nerves. 

 (After His) 529 



228. Transverse section across the medulla oblongata of a human embryo 



lettered by Professor His, Ko, and estimated as thirty-one days 

 old. The section passes through one of the roots of the hypo- 

 glossal nerve, and through both the motor and sensory roots of 

 the pneumogastric nerve. (After His) 532 



229. The left auditory vesicle of a human embryo four weeks old. (After 



W. His, jun.) 542 



230. The left auditory vesicle of a human embryo five weeks old. (After 



W. His, jun.) 542 



231. The left auditory vesicle, or internal ear, of a human embryo of the 



eighth week. (After W. His, jun.) 543 



232. Human embryo lettered by Professor His, Lg, and estimated as 



fifteen days old. The brain and heart are exposed from the 

 right side ; the alimentary canal and the yolk-stalk are repre- 

 sented in median sagittal section. (After His) .... 545 



233. Outline figure of the alimentary canal of a human embryo lettered 



by Professor His, Pr, and estimated as twenty-eight days old. 

 (From His) . 546 



234. Outline figure of the alimentary canal of a human embryo lettered 



by Professor His, Sch, and estimated as thirty-five days old. 

 (From His) 547 



235. Outline figure of the alimentary canal of a human embryo estimated 



as thirty-two days old. (From His) 548 



236. Outline figure of the alimentary canal of a human embryo estimated 



as thirty-five days old. (From His) 548 



237. The floor of the pharynx of a human embryo fifteen days old, seen 



from above. (After His) . . . . ' . . . . 550 



238. The floor of the pharynx of a human embryo twenty-three days old, 



seen from above. (After His) 551 



2 39. The floor of the pharynx of a human embryo twenty-eight days 



old, seen from above. (After His) 552 



240. The head and neck of a human embryo thirty-two days old, seen 



from the ventral surface. (After His) 553 



241. The roof of the mouth of a human embryo about two and a half 



months old, showing the formation of the palate. (After His) . 554 



242. The tongue and the floor of the mouth of a human embryo at the 



end of the second month. (After His) 556 



243. Human embryo lettered by Professor His, Bl, and estimated as 



twenty -three days old. The brain and spinal ' cord are exposed 

 from the right side; and the body is dissected to show the 

 heart, the blood-vessels, and the alimentary canal. (After His) 567 



