THE AGE OF THE FCETUS 23 



larger, branches. These run into two veins at the beginning 

 of the umbilical cord, becoming confluent in the umbilical 

 ring. The umbilical vein returns to the foetus the blood 

 aerated in the placenta ; it has no valves. The blood vessels 

 of the umbilical cord have a strong muscular wall, therefore 

 contracting strongly when ruptured, as is the case at birth. 

 The umbilical vessels of the calf are not all adhering to 

 the umbilical ring, as is the case in other domestic animals. 

 Only the vein is firmly attached. The umbilical arteries are 

 united to the surroundings by loose connective tissue, and may 

 be moved about in the umbilical ring. On tearing of the 

 umbilical cord, they are severed within the abdominal cavity, 

 or, rather, the peripheral end retracts within the abdominal 

 cavity. (Franck.) 



The flat, longish membrane (8 to 12 cm.) seen to hang 

 from the navel of newly born calves, consists of the umbilical 

 cord's sheath and umbilical veins. The knowledge of this 

 condition is of the greatest moment in the aetiology of 

 omphalitis. 



In a calf of 30 kg., the length of the umbilical cord was 

 21 cm., the length of the calf 98 cm., and the weight of the 

 placenta 5| kg. 



The umbilical vessels during the first half of gestation are 

 stretched, while in the second half they are slightly, twisted. 



2.— The Age of the Foetus. 



The age of the foetus is of importance for several reasons. 

 It may be desirable to exactly define it at a forensic examina- 

 tion. Also, in premature birth (partus prcematurus) the knowl- 

 edge of the various sizes of the foetus as regards the period of 

 gestation is of great importance. 



Gurlt first gave definite rules enabling deductions as to 

 the age of the foetus. He divides pregnancy into seven 

 unequal periods. Franck more practically describes the 

 changes which take place each month in the foetus. St. Cyr 

 and Violet, by using the works of Chauveau and Arloing, 



