62 ADMONT H. CLARK 



plexuses are at first distinct connecting with each other only 

 through the lymph sac which makes their conmion point of origin. 

 Soon anastomoses between these primary plexuses connect them 

 so abundantly that the entire surface of the body is covered with 

 a primary and continuous plexus of lymphatics all of which can 

 be injected from any one point. The subsequent development of 

 valves follows the pattern of the original primary ducts as can 

 be seen in figure 505 in the Handbuch der Entwicklungsgeschichte 

 des Menschen, Keibel and Mall, p. 708, 1911, to such an extent 

 that the primary'' lines of growth can be made out in injections. 

 The study shows exactly what is meant by saying that the jugular 

 lymph sac becomes transformed into lymph glands. The glands 

 which arise from the sac itself we call primary lymph glands, those 

 which develop on the vessels which grow from the sac may be 

 called secondary and tertiary glands. The three kinds of glands 

 are all shown in figure 4. Lymph glands develop at the points 

 from which the peripheral lymphatics radiate out. 



