DEVELOPMENT OF SUBOCULAR LYMPH SACS 21 



By injecting into the subocular lymph sacs of the living trout 

 embryo, as well as into other lymphatics (lymphatic of the 

 lateral line of the trunk and lateral pharyngeal lymphatic), or, 

 into the caudal artery or caudal vein, the following observations 

 have been made: 



1. The subocular lymph sacs of the trout do not communicate with 

 each other. 



2. The subocular lymph sacs of the trout do not communicate with 

 the veins, nor with any other lymphatic vessel during the earlier 

 stages of their development (figs. 1 to 9, inclusive). 



In the steelhead and rainbow trout embryos for a period of 

 from five to seven days after fertilization, and in the brook trout 

 for a relatively longer period, each subocular lymph sac serves 

 as a local and independent reservoir for the reception of lymph 

 which it receives from the head region. This lymph is tempo- 

 rarily retained by the sac until it establishes a connection with 

 the lateral pharyngeal lymphatic through which the sac then 

 drains into the veins. Prior to the establishment of this con- 

 nection with the lateral pharyngeal lymphatic, it has thus far 

 proved impossible either to inject the subocular lymph sacs by 

 way of the lateral pharyngeal lymphatic or the veins, or, to 

 inject the lateral pharyngeal lymphatic or the veins by inject- 

 ing into the subocular sacs. 



Figure 18 is a photograph of a Spalteholz preparation of a 

 twenty-day rainbow trout embryo (ventral view) on which the 

 attempt was made to inject the lymphatic system by way of the 

 subocular lymph sacs. The photograph shows that the sub- 

 ocular lymph sacs alone have received the injecta and that none 

 of it has passed from the sacs into the lateral pharyngeal lym- 

 phatic or into the veins. Sixteen injections of this character 

 were made of the subocular lymph sacs of the trout during the 

 early stages of their development, and in three cases the injecta 

 was observed to pass into the veins. On sectioning these three 

 embryos, however, it was found that the inner wall of the sac had, 

 in each case, been punctured by the cannula and that the injecta 

 had extravasated into the capillaries and the veins. In other 

 cases in which the injecta was forced into the subocular lymph 



