Lymphatics in Small Intestine of the Pig. 99 



and abdominal viscera. By injecting into the wall of the intestine 

 only the lymphatics of the intestine and the mesenteric lymph 

 nodes were filled with the injection mass. 



The lymphatics w^ere studied both macroscopically and micro- 

 scopically. In the younger stages, 2.7 to 12 cm., in which a general 

 lymphatic injection was made, a single embryo could be used for 

 both purposes. The best view of the lymphatics is obtained while 

 injecting; there is absolutely no difficulty in distinguishing the 

 lymphatics nor in telling any extravasations whatever. After noting 

 the extent of the injection, small pieces were removed for microscopic 

 sections, while the rest of the embryo was placed in a large amount 

 of strong alcohol, 95 to 96 per cent, until shriveled, then cleared 

 in caustic potash, 1 to 2 per cent, and mounted in glycerine, ac- 

 cording to the Schultze method. 



Specimens cleared in this way show the course of the lymphatics 

 beautifully and with a dissecting microscope they can be followed to 

 all the organs. The walls of the lymphatic vessels are so delicate, 

 however, that the specimens are not permanent 



For the study of the lymphatics of the intestine, cleared pieces 

 of the intestine were mounted in glycerine in hanging drop slides 

 and studied with the microscope in conjunction with serial sections. 

 The portion of the intestine which was most readily identified and 

 which was in all cases particularly examined is a loop of the 

 duodenum which coils around the root of the mesentery. This loop 

 is seen in Tigs. 1, 3 and 4. It is the loop most apt to be injected 

 if the needle is introduced into the thoracic duct, probably for 

 mechanical reasons, for when the needle enters the retroperitoneal 

 sac itself, the mesentery becomes uniformly injected. 



General Description. The lymphatics of the intestine arise from 

 the retroperitoneal sac. This sac is shown in Fig. 1 in an embryo* 

 3 cm. long. The specimen was made by injecting into the thoracic 

 duct. It will be seen that the sac is triangular in shape and lies 

 opposite the hilum of the Wolffian bodies. In an embryo 2.7 cm. 

 long the sac measures about 2 mm. in length, at this stage 3 cm., 

 it is about 2.7 mm. long. That it is connected with the cistema 

 chyli is proved by the injection and is shown in Bsetjer's Fig. 9 

 for an embryo of the same stage. 



