8 LYMPHATICS IN THE STOMACH OF THE EMBRYO PIG. 



at the esophageal opening, at the center of the lesser curvature, and at the pylorus. 

 It is from this mass of lymphatics that most of the gastric vessels develop. It will 

 be noted in the figure that the lymphatics to the esophageal opening already suggest 

 the ring which is later to become so characteristic. The central mass to the lesser 

 curvature can be seen emerging from behind the hepatic vessels which are cut off 

 in the drawing. These vessels to the lesser curvature are shown spreading out over 

 the anterior surface of the stomach ; they also extend over the corresponding area 

 on the posterior wall. Two or three small vessels (P. V.) pass forward to the 

 pylorus and it is important to note that they always reach this structure at its 

 posterior wall. It is these vessels which will later anastomose with both the ascend- 

 ing duodenal vessels (A. Duo. V.) and the vessels of the greater curvature (V. G. C.), 

 as shown in figure 4. 



Growth is very rapid and in slightly older specimens (35 to 45 mm.), in which 

 the splenic vessels have also appeared, the rapid invasion from the lesser cuvature is 

 apparent. The vessels reaching the esophagus have by this time formed a complete 

 subserous, periesophageal ring. This ring continues to develop and in older speci- 

 mens forms a dense, circular plexus around the esophagus, from which branches pass 

 in all directions to ramify over the stomach wall (fig. 8). The annular structure of 

 this plexus is not only manifest as a subserous set of vessels, but is maintained in 

 the depths of the stomach wall in this region as development proceeds. 



The vessels which reach the stomach at the center of the lesser curvature are 

 by far the most numerous of any of the groups. As they traverse the gastro- 

 hepatic ligament they are in direct communication with the lymphatics of the liver, 

 which pass through this structure and also take origin from the retroperitoneal sac 

 (fig. 2) . On reaching the stomach they branch over both the anterior and posterior 

 walls and form numerous anastomoses with the vessels from the esophageal ring, 

 as well as with the lymphatics reaching the lesser curvature at the pylorus. These 

 pyloric vessels form the smallest group of lymphatics invading the stomach. They 

 spring from the right trunk just lateral to the large group at the center of the lesser 

 curvature and pass through the gastro-hepatic ligament to the posterior surface of 

 the pylorus, over which they anastomose freely with the set of vessels reaching the 

 pylorus by way of the mesentery of the duodenum. 



This latter set of lymphatics (fig. 4), to which we may refer as the ascending 

 duodenal vessels, forms a trunk of considerable size. They can be injected only in 

 the younger embryos, due to the fact that one or more lymph glands are later 

 formed in the mesentery of the duodenum at the pyloro-duodenal junction. Their 

 rich anastomosis with the other gastric vessels presents a subject of unusual interest, 

 inasmuch as it is not generally stated that lymphatic drainage of the stomach takes 

 place partly by way of the mesentery of the duodenum. The magnitude of early 

 vessels invading the stomach from this source and the extent of their anastomoses 

 with the gastric vessels proper give proof of a well-defined pathway by which 

 lymphatic drainage from the stomach may take place. Figures 4 and 6 show the 

 extent of the anastomosis of these ascending duodenal vessels with the other vessels 

 of the pylorus. 



