Lymphatics in Small Intestine of the Pig. 97 



is done as follows: The embryo is thoroughly opened and the two 

 Wolffian bodies spread apart as far as possible and the entire in- 

 testine turned to the right. This exposes the sac, as can be seen 

 in Fig. 3. By looking closely one can see three or four small arteries 



Fig. 3. — Embryo pig 3.5 cm. long to show au injection of tlie retroperitoneal 

 sac made through the thoracic duct, x 2.5. r. s., retroperitoneal sac ; r. c, 

 reproductive organ ; s, stomach ; W. b., Wolffian body. 



to the Wolffian body running perpendicular to the rectum ; the needle 

 must enter just dorsal to these arteries. The retroperitoneal sac 

 is the best point for injecting the viscera. To determine the zones 

 in the intestine, the sac has been filled until it ruptured. Good 

 injections are only to be obtained in embryos in which the heart is 



