100 CARNEGIE INSTITUTION OF WASHINGTON. 



aorta. The retroperitoneal sac lies outside of the peritoneal cavity, 

 between the Wolffian ducts and the gonads, and extends from the re- 

 gion of the coeliac axis to the bifurcation of the aorta. In general, it 

 may be said that the lymphatics of all the structures situated within 

 the abdominal cavity arise from this ventral sac. The iliac sacs are 

 situated on either side of the midline, between the aorta and the kidneys, 

 and are connected with the jugular sac by the thoracic duct and the 

 cisterna chyli. In the early stages they appear to be united and form 

 a rectangular sac between the medial surfaces of the kidneys. 



From the retroperitoneal sac are given off lymphatics which drain 

 in whole or in part the lungs, diaphragm, liver and biliary passages, 

 stomach, small intestine, capsule of spleen, pancreas, kidneys. Wolff- 

 ian bodies, gonads, Miillerian and Wolffian ducts, and umbilical cord. 

 From the iliac sacs lymphatics drain in whole or in part the diaphragm, 

 body wall, adrenals, kidneys, bladder, Miillerian and Wolffian ducts, 

 umbihcal cord, and the entire posterior half of the body. Only a few 

 structures, notably the diaphragm, kidneys, and Miillerian and Wolff- 

 ian ducts, which later become the excretory canals of the sex glands, 

 receive vessels arising from both the retroperitoneal and iliac sacs. 



It is of interest to note that the diaphragm is provided with a double 

 drainage, which is probably explained by its double origin. Large 

 lymphatic vessels from the lower lobes of the lungs extend to the pillars 

 of the diaphragm. Other vessels from the plexus of the lesser curvature 

 of the stomach pass directly to the diaphragm along the hepatic Uga- 

 ments, anastomosing freely with the pulmonary vessels. Reichert's 

 observations in this respect confirm those of Cash and of Cunningham, 

 which have been previously referred to. 



The early system of drainage was found by Reichert to continue into 

 the later stages of development. Embryos of 20 cm. were injected, 

 the injections being as nearly complete as possible, in order to deter- 

 mine which glands receive the drainage from the abdominal and the 

 pelvic viscera. The primary sacs by this time have changed to lymph 

 glands and receive afferent vessels from the same organs and structures 

 as did the parent sac. Generally speaking, these lymph glands, as 

 concerns position, may be divided into two groups: those ventral and 

 ventro-lateral to the aorta, and those dorsal and dorso-lateral to the 

 aorta. Here, as in the primary system, it may be said that the organs 

 and structures lying within the abdominal cavity, as well as the entire 

 posterior half of the body, drain into the glands dorsal or dorso-lateral 

 to the aorta. 



A paper on the digestion tract has been completed by Dr. P. E. 

 Lineback, who has studied the development of the longitudinal-muscle 

 layer of the colon in human embryos, and a preliminary paper on the 

 digestion tract of the opossum has been pubHshed by Dr. C. H. Heuser. 

 Dr. Heuser's work was started while he was at the Wistar Institute and 



