LYMPHATICS IN THE STOMACH OF THE EMBRYO PIG. 7 



traverses the gastro-splenic ligament to the center of the greater curvature of the 

 stomach where it ramifies to right and left (fig. 4). These lymphatics then anasto- 

 mose, over both the anterior and the posterior walls, with those from the lesser 

 curvature, where connections are formed with the lymphatics of the esophagus and 

 duodenum (cf. figures 4 and 5, plate 1). 



After this brief description of the general pathways along which lymphatic 

 invasion of the stomach takes place, the characteristics of each invading set of 

 vessels and their part in forming the general lymphatic plexuses remain to be 

 considered. 



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TEXT-FIO. 3. Pig embryo, 

 100 mm. long. Dia- 

 grammatic transverse sec- 

 tion of the stomach and 

 spleen with their perito- 

 neal ligaments. The ar- 

 rows which begin from the 

 retroperitoneal sac show 

 the directions in which 

 lymphatic invasion of the 

 stomach takes place. In 

 this specimen the stomach 

 is collapsed. The hilum 

 of the spleen is marked by 

 vessels of the splenic mes- 

 entery (V. S. M.); also 

 the greater curvature of 

 the stomach may be 

 located both by its vessels 

 (V. G. C.) cut in cross- 

 section and by the attach- 

 ment of the gastro-splenic 

 ligament. 



The stomach may be regarded as being invaded from the posterior side at the 

 lesser curvature by the right trunk, and anteriorly along the greater curvature 

 by the left trunk. The posterior invasion of the lesser curvature takes place 

 along the gastro-hepatic ligament (the primitive ventral mesentery), while the 

 anterior invasion at the greater curvature is by way of the splenic and gastro- 

 splenic ligaments (the primitive dorsal mesentery of the stomach) and the mesentery 

 of the duodenum (text-figure 3). This arrangement offers a striking contrast to 

 the manner in which the lymphatics reach the intestine. Here, straight trunks 

 grow out from the retroperitoneal sac through the mesentery and, on reaching the 

 wall of the intestine, divide into right and left branches to surround the gut. In the 

 case of the stomach the right and left branches leave the retroperitoneal sac directly 

 and pass to the stomach by way of two separate folds of related peritoneum. 



The earliest stage injected was an embryo 28 mm. in length (fig. 7). The 

 vessels arising from the retroperitoneal sac can be seen just reaching the stomach. 

 This is a very early stage and the injected vessels are those arising from the right 

 gastric trunk of the retroperitoneal sac. In this specimen the spleen and liver have 

 been removed. It has never been possible to inject the splenic vessels (left gastric 

 trunk) at this stage, but the mode of entrance of the right gastric trunk is well 

 illustrated. Figure 7 shows the primitive mass of lymphatics which later becomes 

 grouped into the right gastric trunk and distributed to the stomach in three parts : 



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