SEX IN" LIVING FORMS 109 



At the end of tlie seventh week, it is three-fourths 

 of an inch long. The liver, lungs, and other internal 

 organs are partially formed. 



At the eighth week, it is about one inch in length. 

 It begins to look some like a human being, but it is 

 impossible to determine the sex. 



At the third month, the embryon has attained the 

 length of from two to two and one-half inches. Its 

 weight is about one ounce. 



At the end of the fourth month, the embryon is 

 called a fetus. It is from four to five inches long, and 

 weighs five ounces. 



At the fifth month, the fetus is nearly a foot long, 

 and weighs about half a pound. 



At the sixth month, the average length of the fetus 

 is about thirteen inches, and its weight one and a half 

 to two pounds. If born, life could continue a few min- 

 utes. 



At the seventh month, the fetus is from fourteen to 

 fifteen inches long, and weighs from two to three 

 pounds. It is now viable (may live if born). 



At the eighth month, the length of the fetus is from 

 fifteen to sixteen inches, and its weight from three to 

 four pounds. 



At the ninth month, the fetus is about seventeen 

 inches long, and weighs from five to six pounds. 



At birth, the infant weighs a little more than seven 

 pounds, the usual range being from four to ten pounds, 

 though these limits are sometimes exceeded. 



Duration of Gestation.— The length of time re- 

 quired for the development of a human being is usually 

 reckoned as about forty weeks. A more precise state- 

 ment places it at about two hundred and seventy-eight 

 days. This limit is often varied from. Cases have 



