Florence E. Sabin 



375 



stage of a dissecting microscope, just enough pressure is used so that 

 Ihe fluid will drop slowly and the needle is screwed down into the side 

 of the neck half way between the ear and the upper border of the arm. 

 If the pig is not longer than 3 cm., tie the umbilical cord so as to fill 

 the veins with blood and then introduce the needle into the side of the 

 neck to a point just outside the anterior cardinal vein. For the point 

 of radiation of the ducts for the lower part of the body, namely, over 

 the crest of the ileum subcutaneous rather than deep injection are 

 better for, as will appear later, the posterior lymph hearts are situated 

 ver}^ deep. 



Ear 



Fig. 1 

 cm. lonj 



Eye 



Terminal lymphatics of the skin between the eye and the ear in a pig 5 

 X 16. 



It now became necessary to study more carefully these successive 

 zones which had been injected, to prove that the ducts in the border 

 of the zones were terminal and to note their relation to the skin areas 

 not yet invaded by lymphatics. Figure 2 gives a picture of the border 

 zone taken from the ducts injected over the side of the head between 

 the "eye and the ear in a pig 5 cm. long. This is a favorable place for 

 study, for the ducts are larger and readily seen with the unaided eye. 

 In general the ducts are the largest in pigs from 4 to 5 cm, long and 

 they decrease in size as the pig grows larger. Other good places for 

 studying the border zone are over the shoulders and over the side of 

 the body. The ducts from the two sides of the neck meet and anasto- 



