LYMPHATICS IN THE STOMACH OF THE EMBRYO PIG. 11 



one of the most striking characteristics of all injections of the stomach made before 

 the appearance of glands in this region. Its formation by vessels arising from the 

 retroperitoneal sac is well shown; branches may be observed passing in every 

 direction from all points of it ; those going to the cardiac pouch are well seen over 

 the anterior wall, while in the depths on the posterior wall are seen the vessels of 

 the left gastric trunk with which they anastomose. Those vessels passing to the 

 anterior wall are shown as a series of parallel trunks in the serosa which lead into 

 the deeper, much more extensive plexus of the submucosa within the depths of the 

 stomach wall. These serosal trunks, as well as the plexus of the submucosa, anasto- 

 mose with the corresponding trunks and plexus arising from the vessels of the greater 

 curvature ; they remind one of similar parallel trunks shown by Heuer in the develop- 

 ment of the lymphatics of the intestine. The posterior surface of the stomach is 

 seen on the left side of the figure. Here the posterior position of the pyloric vessels 

 arising from the lesser curvature is well shown, as is also the characteristic arrange- 

 ment of the serosal trunks and plexuses of the submucosa. 



The development of lymphatics of the diaphragm is likewise well illustrated by 

 these injections. Large lymphatic trunks, accompanied by the lymphatics of the 

 lower lobes of the lungs which arise from this source, can be seen passing from the 

 anterior part of the retroperitoneal sac to the pillars of the diaphragm. The 

 pulmonary vessels penetrate the diaphragm, while the others spread out over its 

 surface. Also from the gastric plexus, at the lesser curvature of the stomach, many 

 large vessels pass directly to the diaphragm along the ligaments of the liver and 

 anastomose freely with those from the retroperitoneal sac, arriving by way of the 

 pillars (fig. 6) . Such an invasion of the diaphragm is readily explained by the double 

 origin of this structure, the pillars arising from the pleuro-peritoneal membrane, 

 while the body of the diaphragm arises from the ventral mesentery, septum trans- 

 versum, and body-wall. The embryonic lymphatics of the diaphragm are enormous 

 and soon cover the entire structure with a dense plexus. The active function of the 

 diaphragm as an agent of absorption is at once apparent by a glance at its rich 

 supply of lymphatics. 



Here a word may be said about the lymphatics of the esophagus and their 

 relation to those of the stomach. Its vessels are derived from two sources. Those 

 of the lower end arise from the gastric vessels forming the periesophageal ring 

 at the cardia of the stomach, from which they spring as direct outgrowths and ex- 

 tend upward to a point on the esophagus about midway between the bifurcation 

 of the bronchi and the cardia of the stomach. Here they meet lymphatics which 

 have extended to the esophagus from the bronchial plexuses at the hilum of the 

 lungs, primarily arising from the thoracic duct. The lymphatic plexuses of the 

 esophagus are completed by the anastomosis of the vessels from these two sources. 

 In their general arrangement they are similar to those of the stomach wall, with 

 which they are continuous. Lymphatic drainage from the esophagus takes place 

 in two directions, the lower portion following the general path for gastric drainage 

 described for the cardia of the stomach, while the upper portion drains to the 

 bronchial plexuses. 



