32 GROWTH 



With spectacles on nose, and pouch on side, 

 His youthful hose well sau'd, a world too wide, 

 For his shrunke shanke, and his bigge manly voice 

 Turning againe toward childish treble pipes, 

 And whistles in his sound. Last scene of all, 

 That ends this strange eventful historie, 

 Is second childishnesse, and meere oblivion, 

 Sans teeth, sans eyes, sans taste, sans everything. 



We shall follow the example set by Shakespeare and em- 

 pirically divide life into seven stages. Instead, however, of 

 beginning with the infant stage of life, we shall begin with the 

 ovum, that is, the egg after fertilization. 



There is no doubt but that the most marvelous changes of 

 the whole life take place during the earliest stage of life, 

 namely, the embryonic stage. This stage comprises in man the 

 first three months of life. During this stage, the ovum, a single 

 cell of less than one seven-hundredth of an inch in diameter 

 has been developed into a body containing practically all the 

 important structures found in adult man. Indeed, during this 

 stage the embryo contains some structures not found in adult 

 man as, for example, gill slits in the third week, and tail in the 

 sixth week. 



The embryonic stage is followed by the fetal stage lasting 

 from the age of three months to the age at birth, which is be- 

 tween nine and ten months after fertilization of the egg. Dur- 

 ing the fetal stage, the parts already formed during the em- 

 bryonic stage grow in weight and maturity, but no new parts 

 are formed. 



Up to the time of birth the embryo, and then the fetus, ob- 

 tains nourishment and oxygen by way of the umbilical cord 

 from the mother's blood by means of a structure known as 

 the placenta (an outgrowth of the outer, or chorion, mem- 

 brane surrounding the embryo), which is attached to the 

 mother's womb. At birth this method of obtaining nourishment 

 and oxygen is abruptly ended. The newly born infant must 



