The Origin and Development of the Lymphatic System. 57 



nective tissue. Knower and Hoyer, however, have found that they 

 bud off from the posterior vertebral veins considerably later than the 

 anterior lymph hearts, and they have been well worked out by 

 Baranski (9). Baranski shows that they arise by several buds from 

 the endothelium of the posterior vertebral vein and its branches. His 

 fig. 1 shows particularly well the heaping up of the endothelium so 

 that it looks like a solid mass at the point of origin. Practically 

 nothing is known of the origin of the deep lymphatics in amphibia. 



It has thus been shown that the lymph hearts of amphibia arise as 

 buds or sacs from the endothelial wall of segmental veins. They lie 

 on the myotomes, from which they derive the striated muscle of their 

 wall. 



The subcutaneous lymph sacs of the anura are secondary structures. 

 This was found out by Eanvier (116) in 1896, and also by Knower 

 and Hoyer. They are derived from ducts which grow from the 

 lymph hearts. They have been comparatively little studied. Hoyer 

 (49) found that the large sac on the ventral surface of the head (sacc. 

 submaxillaris) developed from a branch of a duct from the anterior 

 lymph heart, and that the lateral sacs are derived from the lateral 

 lymph trunks. 



This point has been just shown in connection with the sacs of the 

 extremities by Frl. Goldfinger (38), who has injected the primary 

 ducts and then the increasingly denser lymphatic plexus up to the final 

 lymph sacs. This process of cavernization could be studied here by 

 silver nitrate injections. 



Since the above was written Hoyer (49a) has published an article 

 in which he gives a general review of the origin of the lymphatic 

 system in vertebrates, and Hoyer and Udziela have given the first 

 comprehensive description of the lymphatic, system in a urodele (49b). 

 In a salamander larva the lymphatic system opens into the veins 

 first through symmetrical axillary lymph sacs or sinuses, and secondly 

 through a series of subcutaneous lymph hearts which pump the lymph 

 into the vena lateralis (Meyer 88a and Marcus 87a) . 



There are six longitudinal lymph trunks, four superficial and two 

 deep (Hoyer 49b, Taf. XII, Pigs. 1, 2 and 5). (1) The median, dor- 

 sal, longitudinal lymph trunk, which extends from the point of the tail 

 to the middle of the head; (2) a medial, ventral caudal trunk, which 

 branches around the cloaca and opens into the inguinal sinus as is 

 shown in fig. 2 (49b) ; (3 and 4) symmetrical lateral trunks, which 



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