OF THE LYMPHATIC SYSTEM OP THE CHICK. 



473 



This operation was repeated a number of times, and by allowing the chicks 

 to incubate for varying periods, we obtained an interesting series of embryos. 



In an operated embryo of 5 days and 15 hours, corresponding to a normal 

 chick of about 5^ days, injection revealed a normal anterior plexus on the left 

 side extending deep into the axilla. As in normal chicks, the lymphatics dorsal to 

 the shoulder had not yet developed. Posteriorly, the lymph-heart region was 

 absent and no lymphatics could be injected over the pelvis. In other words, the 

 condition of lymphatics was identical with that found in embryos after operation 1. 



On the right side, where the double operation had been performed, the lym- 

 phatic plexus anterior to the gap was present and normal in appearance. It extended 

 from the deep jugular plexus connecting with the veins, posteriorly through the 



12 



FIG. 10. Left side of an embryo of 6 days and 15 hours. Normal except for the absence of the tail. Superficial lymphatic 

 plexus injected. Control for right (operated) side shown in figures 11 and 12. X 12. 



FIG. 11. Right (operated) side of a chick of 6 days and 15 hours. Same embryo as in figure 9. Large gap present in body- 

 wall extending to mid-line of the back, leaving spinal cord exposed. Embryo twisted toward left side. Lymphatic 

 plexus injected dorsal to shoulder and in axillary region normal. Posteriorly, lymphatic plexus injected on pos- 

 terior half of pelvis and around the stump (fig. 12). Normal in character. No lymphatics injected over anterior 

 part of pelvis. X 12. 



FIG. 12. Posterior view of the same embryo shown in figures 10 and 11, showing the lymphatic plexus extending around the 

 tail-stump from both sides. X 12. 



axilla, and ended just anterior to the gap in fine delicate points, smaller than the 

 vessels usually found in this region. Posterior to the gap i. e., over the leg and 

 pelvis as on the opposite side no lymphatics could be injected. 



The next stage found in this experiment is that which has already been 

 described the chick pictured in figures 8 and 9. 



In the next stage (an embryo of 6 days and 15 hours) the left side showed a 

 luxuriant lymphatic plexus from the axilla, over the side, the pelvis and almost 



