LYMPH-FLOW AND LYMPHATICS, CHICK EMBRYOS 413 



the veins. In this stage also the remainder of the blood is washed 

 out of the superficial lymphatic system. The character of the 

 lymphatics and the direction of lymph-flow for this stage are 

 illustrated in figure 3. 



In chicks a little younger than 7 days (measuring 19 to 20 

 mm.) ink granules injected into the posterior portion of the 



Fig. 3 Chick of 6^ days (18 mm.) . Stage of beginning lymph heart pulsations 

 and earliest posterior circulation over the pelvis, and of beginning anterior flow 

 of lymph in the supra-scapular plexus. Injection shows first posterior channels 

 and the first supra-scapular channel differentiating from the primary plexuses. 

 L.H., lymph heart which begins to pulsate while still in the form of a plexus. X 5. 



supra-scapular lymphatic plexus make their way slowly poste- 

 riorly, pursuing a winding course to the side lymphatics. From 

 here they move on posteriorly, more rapidly and directly, over 

 the side and pelvis and into the lymph heart, whose pulsations 

 have become stronger. The only parts of the superficial lym- 

 phatics in which the circulation is still anterior, at this stage, are 

 the region just posterior to the shoulder, where the granules 



