368 The Development of the Lymphatic System 



Having repeated Budge's experiments I am convinced that while 

 his injections of the ducts along the arteries are fundamental in the 

 study of a certain stage of the development of lymphatics, the spaces 

 connected with the false amnion have no connection whatever with 

 the lymphatic system. In injecting the false amnion some minor 

 changes in the methods of Budge are an advantage. Instead of a 

 hypodermic syringe it is better to use a glass tube drawn out to a 

 fine point and to introduce the fluid slowly under the even pressure 

 of a low column of mercury. Budge used Berlin blue and found it 

 necessary after filling the false amnion, to stroke the embryo gently in 

 order to force the fluid into the area vascnlosa. India ink is, however, a 

 better fluid, for it is so finely divided that it runs of its own accord. I 

 inserted the needle into the false amnion according to Budge's direc- 

 tions, given in his first paper, and injected the ink until the cavity 

 was jnst full, then floated the embryo on to a glass slide with the 

 dorsal surface upward. The fluid will now enter the area vascnlosa 

 and in places will run to its edge. This can be watched under the 

 microscope. The fluid runs by putting out blunt processes simulating 

 canals and so interpreted by Budge; at first these processes anasto- 

 mose, making the network shown in Budge's pictures, but, as a rule, 

 the meshes soon fill in and the fluid advances as a solid column with 

 processes projecting in every direction. In other words, the fluid 

 runs just as it would if forced between two glass plates held closely 

 together. In serial sections through these injected specimens it is 

 found that the upper and lower layers of the area vascnlosa are con- 

 nected here and there by delicate fibrils which are really processes 

 of. scattered mesenchyme cells and that the injected fluid passes into 

 the spaces thus made and not into preformed channels lined by endo- 

 thelium. 



jSk)twithstanding the fact that Budge's theory of the origin of the 

 thoracic duct is not correct, this theory led to the discovery of the 

 true origin. For it was by injecting into the side of the neck in 

 early embryos in the hope of reaching Budge's spaces behind the 

 aorta, that the cervical lymph heart was injected, and the lymph 

 hearts give the key to all the superflcial lymphatics. 



Between the years 1895 and 1897, Eanvier published a long series 

 of articles on the development of the lymphatic system. He worked 

 chiefly on the frog, and on pig embryos from 9 to 18 cm. long. From 

 his injections of the lymphatic capillaries in the skin and in the villi 

 of the pig embryos he made an important discovery; namely, that the 

 lymphatics within the capillary plexus grow by budding. He says that 



