272 PHYSIOLOGY CHAP. 



For the determination of the length of the foetus, measured 

 from the crown of the head to the heel of the foot, Haase suggested 

 the following mnemonic device as easy of application in obstetric 

 and medical legal practice : 



At the end of the first month = 1 x 1 - 1 cm. 



In order to facilitate as far as possible for embryologists and 

 physiologists the diagnosis of the age of the human embryo and 

 foetus, I think it useful to give the table drawn up by my 

 predecessor Jacob Moleschott, which in his own handwriting 

 hangs on the wall of the room containing the embryological 

 collection of the Physiological Institute of Rome. In this table 

 it will be seen that the numerical data of foetal length and 

 weight vary within somewhat wider limits than those given by 

 Hecker and Ahlfeld ; it also gives certain external characteristics 

 of the embryo as guides for the -more accurate estimation of the 

 stage of development during the successive weeks and lunar 

 months : 



TABLE FOU THE DIAGNOSIS OF THE AGE OF THE HUMAN EMBRYO 

 AND FOETUS COMPILED BY JACOB MOLESCHOTT 



First month. Second week Ovum 6'7 mm. Embryo 2*2 mm. Closure 

 of medullary tube commenced, heart initiated ; corresponds to end of first 

 day of embryo chick. 



Third week. Ovum 13'5-27 mm. Embryo 4'5 mm. Three cerebral 

 vesicles, three branchial fissures. Umbilical vesicle ; corresponds to third 

 day of chick. 



Fourth week. Ovum 18 - 27 mm. Embryo 8 mm. Quadrigeminal 

 eminence, four- branchial fissures, stumps of limbs, greatest curvature of 

 embryo ; head and tail touch ; closure of intestine except the orifice of the 

 omphalo-mesenteric canal ; loup of intestine projects outside the abdomen. 



Second month. Fifth week. Embryo 12 mm. Choroid fissure, nasal 

 fossa, branchial fissures reduced to grooves. The embryo begins to straighten 

 itself; hand and foot, but the humerus of the arm and the femur of the leg 

 cannot be distinguished ; the abdominal wall is closed with the exception of 

 the umbilical ring ; umbilical cord ; the placenta begins. 



Sixth week. Embryo 16 mm. Branchial grooves have disappeared ; nasal 

 aperture separated from mouth, although the palate is wanting ; thorax and 

 abdomen. 



Seventh week Embryo 20 mm. Eyelids, ears, nose, tongue ; disappearance 

 of choroid fissure ; fingers and toes begin as little furrows ; omphalo-mesenteric 

 canal obliterated. 



