56 Florence B. Sabin. 



muscle (where there are no lymphatics, only tissue spaces) traveled 

 exceedingly slowly; on the other hand, a small amount of the fluid 

 injected into a lymph sac traveled rapidly, but in a zone limited ex- 

 clusively to the lymph sacs, according to their anatomical conections. 

 When the dye reached the lymph heart in the cardiectomized frog 

 it was pumped, not through the heart to the systemic vessels, but 

 through the vertebral veins to the nervous system. Thus is explained 

 the marked effect of the small dose. If the lymph hearts were killed 

 the convulsions did not take place. 



It has been shown that the anterior lymph hearts of the amphibia 

 bud off from the vetebral veins (Hoyer 49), or in a more primitive 

 position from branches of the earlier segmental veins which are going 

 to form the vertebrals (Knower 74). They develop earlier than the 

 posterior hearts and have been found in B. palustris, B. sylvatica and 

 E. virescens measuring about 6.5 mm., and in E. temporaria and 

 Bufo vulgaris measuring about 4.5 mm. Hoyer noted the presence 

 of blood in the early stages of both anterior and posterior hearts. 

 Knower brings out the fact in connection with the anterior hearts 

 that they lie on the myotomes from which they derive the striated 

 muscle of their wall. This is, I think, a very important point. The 

 particular myotome Knower has shown may vary. 



The pulsations of the anterior lymph hearts can be readily seen in 

 the dorsal surface of the tadpole, just behind the pronephros, and thus 

 they can be injected. 



Prom the anterior lymph heart develop two symmetrical vessels, 

 one of which runs forward toward the head, the other backward toward 

 the tail. The posterior duet as described by Hoyer divides into two 

 branches, one running to the tip of the tail dorsal to the myotomes, 

 the other passing back along the ventral margins of the myotomes 

 to form the ventral caudal trunk. It is the branches of these two 

 caudal trunks which have been studied so much in the living specimen. 

 There is also a lateral branch which runs caudalward from the an- 

 terior lymph hearts on the lateral surface of the myotomes half way 

 between the dorsal and ventral branches. This lateral trunk subse- 

 quently connects with the posterior lymph heart. 



Wieliky (153), Jossifov (62-65), and Favaro (36) thought that the 

 posterior lymph heart arose from the dilation of the caudal lymph 

 trunks which grow from the anterior lymph hearts, -and Jourdain 

 (61) describes them as being formed by a rapid destruction of con- 



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