viii ILLUSTRATIONS 



Fig. 17. The individual and evolutionary development of the 



nerve cell 49 



Fig. 18. Section through the spinal cord showing the early de- 

 velopment of a spinal nerve .... facing page 50 



Fig. 19. Organs developing from the rudimentary alimentary 



canal 52 



Fig. 20. The development of the human heart 54 



Fig. 21. The development of the face of a human embryo (His) 



facing page 56 



Fig. 22. The relation of the fetal to the maternal blood in the 



human placenta facing page 58 



Fig. 23. Comparison of the embryos of various mammals at 



corresponding stages of development . facing page 62 



Fig. 24. Changes in proportion during growth 66 



Fig. 25. Growth curves for increase in weight and stature in 



both sexes 68 



Fig. 26. The caecum and vermiform appendix in various mam- 

 mals 74 



Fig. 27. Supernumerary nipples of man 77 



