xii CONTENTS 



Factors which modify growth, 246 



Growth of embryonic tissues, 247 



Limitation of growth, 248 



Growth of organs, 248 



Cellular growth, 249 



Self-duplicating units, 250 



Raw materials for growth, 251 



Energy sources, 253 



Respiration of the embryo, 254 



Excretion in embryonic development, 255 



18 • HORMONES AND THE GROWTH OF THE MAMMALIAN EMBRYO 257 



The ovarian cycle, 259 

 The uterine cycle, 259 

 Control of the cycles, 260 

 Pregnancy, 261 

 Placental hormones, 262 

 Vitamin E, 264 



19 • MAMMALIAN DEVELOPMENT 265 



Early development, 266 



Comparison of chick and pig embryos, 270 



Human development, 273 



Human embryo at three weeks, 274 



Development from three to four weeks, 277 



Human embryo at six weeks, 279 



Onset of muscular contraction, 280 



The human embryo at eight weeks, 281 



The human fetus at twelve weeks, 283 



The development of reflexes, 284 



Development from 20 to 38 weeks, 286 



Birth, 289 



Principles of human development, 293 



20 • SEX DIFFERENTIATION 295 



SUGGESTED READINGS 307 



INDEX 315 



