LYMPHATICS IN THE STOMACH OF THE EMBRYO PIG. 13 



subserous plexuses were found to be rather scanty and mostly on the posterior walls 

 of these organs, while the submucous anastomoses were quite numerous. 



Such observations are in strict accordance with the ideas one would be led to 

 form from a study of the development of the gastric lymphatics. The three points 

 of invasion from the lesser curvature correspond to the chains of glands along the 

 ascending and descending branches of the coronary artery and the hepatic artery. 

 The lymphatics reaching the stomach by way of the splenic ligaments, however, 

 appear to indicate that lymphatic invasion does not always take place along blood- 

 vessels, since the lymphatics traversing these ligaments are not accompanied by any 

 blood-vessels of appreciable size. More likely, it seems that related folds of perito- 

 neum determine the pathways by which the lymphatics reach the stomach; in many 

 cases the arteries take the same course. The greater number of anastomoses 

 between the vessels of the pylorus and duodenum than has commonly been observed, 

 and the fact that most of the connections between the subserous plexuses of these 

 organs are located on their posterior walls, are points which can be readily under- 

 stood from the development of the ascending duodenal group of vessels, which 

 are much more numerous in this region (figs. 4 and 6). 



So, from the combined evidence offered by injections of developing lymphatics 

 in several embryonic stages, and the further injection of these vessels after the 

 lymphatic plexuses of the stomach have been completely formed, the lymphatic 

 supply of this organ is seen to be one of the richest in the entire body. Due to the 

 homogeneity of its plexuses, no strict division of its areas of drainage can be made 

 that will remain constant in any number of cases. So readily is any portion of the 

 stomach injected from any other part that, in all probability, the lymphatics of 

 the entire organ could be filled by a single injection into the submucosal plexus, if 

 performed slowly enough and with proper pressure. The greatest part of the 

 gastric drainage certainly takes place by way of the lesser curvature, but the other 

 two routes by way of the splenic ligaments and duodenal vessels are of quite ap- 

 preciable capacity. Many factors, such as peristalsis, muscle tone, venous engorge- 

 ment, pressure in the lymphatic vessels themselves, and (in pathological stomachs) 

 various degrees of obstruction must determine the relative amount of drainage by 

 these three outlets, the sources of whose output are in continuity and show no zonal 

 lines of demarcation. 



