DISSECTION OF THE PIG EMBRYO 39 



and connection of the embryo to the chorion. Label all the 

 parts. 



Carefully remove the entire chorion from the uterus. 

 It will be seen that the only connection of the embryo to 

 the uterus is the contact of the chorion and the mucous 

 lining of the uterus. Open the amnion on the dorsal side 

 of the embryo. It will be seen that it is not connected 

 with the embryo except at the distal end of the umbilical 

 cord. How many blood vessels in the umbilical cord? 

 The blood vessels may be distinguished from the re- 

 mainder of the tissue in the umbilical cord by their dark 

 color, due to the blood in them. The colorless tube in 

 the umbilicus is the allantois. 



3. The Dissection of the Embryo 

 a. The Abdomen 



Cut aw^ay the amnion and the chorion except for a 

 small part at the end of the umbilicus. Open the em- 

 bryo in the mid-ventral line, being careful to separate 

 the tissue from the umbilicus. Do not break any of the 

 blood vessels or the allantois. Pin back the body wall. 

 The large, reddish-brown mass exposed is the liver. 

 Separate the blood vessels in the umbilicus and trace 

 them into the body. The one going to the liver is the 

 umbilical vein. The other two are the umbilical arteries. 

 Trace the allantois toward the posterior end. The en- 

 largement of the allantois in the pelvic region is the uri- 

 nary bladder. A tube from either side enters the bladder 

 on the dorsal surface near the posterior end. These are 

 the ureters. Separate the tube leading from the bladder 



