HUMAN EMBRYO AND FETAL MEMBRANES 



The following are the estimated ages and lengths of human embryos, 

 according to Mall, and their weights according to Jackson. 



Crown-rump length Crown-heel length 

 (CR) , or sitting (CH) , or standing 

 height (mm.). height (mm.). 



Twenty-one days 



Twenty-eight days 



Thirty-five days 



Forty-two days 



Forty-nine days 



Second lunar month . . . 



Third lunar month 



Fourth lunar month . . . 



Fifth lunar month 



Sixth lunar month 



Seventh lunar month . . 

 Eighth lunar month . . . 

 Ninth lunar month .... 

 Tenth lunar month . . 



o-5 



2-5 



5- 5 



II. O 



17.0 

 25-0 

 68.0 



121 .0 



167 .o 



2IO.O 



245.0 

 284.0 

 3l6.0 



345-Q 



o-5 



2-5 



5-5 



II. O 



19.0 



30.0 



98.0 



180.0 



250.0 



370.0 

 425.0 

 470.0 

 ;oo.o 



Weight 



.04 



3 

 36 



120 



330 



635 



I22O 



1700 



2240 



3200 



For comparison and reference the gestation periods of a few representative mammals 

 innended : 



are appended: 



Opossum 13 days 



Mouse 20 days 



Rat 21 days 



Rabbit 30 days 



Cat.... 8 weeks 



Dog, guinea pig 9 weeks 



