LYMPHATICS IN THE STOMACH OF THE EMBRYO PIG. 5 



points at which they reach the stomach, their manner of growth, their anastomoses, 

 and finally the relation of the gastric lymphatics to the lymphatics of other organs 

 can be observed. Embryos 40, 60, 80, and 120 mm. in length were used. Those 

 up to 90 mm. were injected through the retroperitoneal sac, or its remains, the 

 large lymphatic plexus of vessels between the Wolffian bodies. In the embryos 

 measuring over 90 mm. the injections were made directly into the submucosal 

 plexus at the lesser curvature, since valves and nodes, forming at this age, prevent 

 retrograde injection of the organ from the retroperitoneal sac. In such a study it 

 would be very helpful to have complete injections of the lymphatics of the adult 

 stomach and its surrounding organs, but the valves and nodes along the course of 

 the vessels act as effective barriers to extensive injections. For a successful 

 injection the embryo must be fresh, preferably with the heart still beating. Hypo- 

 dermic syringes of 1 c. c. capacity with fine needles (No 28), were used for inject- 

 ing. The best specimens were obtained with a saturated aqueous solution of 

 Berlin blue as the injection mass. Most of the material was cleared in oil of winter- 

 green by the Spalteholz method. Thick microscopic sections were cut to show the 

 progressive development of the plexuses within the stomach wall and the course of 

 the vessels which traverse the ligaments of the spleen. The actual technique of 

 injecting the retroperitoneal sac has been described by Baetjer (1908) in his work 

 on the morphology of that structure and need not be repeated here. 



In their development the lymphatics of the stomach pass to it by way of its re- 

 lated folds of peritoneum. Therefore, a clear idea of the relation of these folds to 

 the stomach, as well as to the points of origin of the lymphatic trunks which invade 

 it, is imperative for an understanding of the development of these vessels. As the 

 relations of this part of the peritoneum in the pig are slightly different from those in 

 the human body, a brief description of them is necessary. The dorsal mesogastrium 

 which later forms the great omentum, contains the spleen between its layers. The 

 spleen lies ventralward, close along the greater curvature of the stomach, and has 

 two ligaments. The first of these is the gastro-splenic, that part of the omentum 

 connecting the spleen with the greater curvature of the stomach. The second is 

 the splenic ligament, that part of the omentum which forms the posterior wall of 

 the omental bursa and from the hilum of the spleen is continuous with the perito- 

 neum covering the Wolffian body, the general mesentery of the intestine and the 

 mesentery of the duodenum. The transverse colon, with its mesentery, lies free from 

 the omentum. The duodenum has a broad, fan-shaped mesentery which continues 

 cephalad to that part of the omentum forming the posterior wall of the omental 

 bursa and caudad to the common mesentery of the small intestine. The ventral 

 mesentery remains as the gastro-hepatic ligament, connecting in the usual manner 

 the lesser curvature of the stomach with the hilum of the liver. 



The retroperitoneal sae, discovered by F. T. Lewis, has been well described by 

 Sabin, Baetjer, Heuer, and other workers in this laboratory. It is a triangular 

 structure which lies at the base of the mesentery at the level of the coeliac axis. 

 There are two small indentations along its sides, made by the adrenal bodies, which 

 thus divide the sac into two lobes. From the posterior lobe, which is the larger, 



