26o THE SALAMANDER 



of a rib. It is usually necessary to dissect away some muscle-fibres 

 in order to expose them fully. Particularly is this so in the trunk 

 region, but behind the sacrum they lie more superficially. 



Lymph is received by each heart from two sources — first, from the 

 T. lymph, long, lateralis, i.e. from the lateral subcutaneous network, 

 and secondly from the parietal branches of the subvertebral trunks. 

 The openings both into and from the hearts are guarded by valves. 

 Figs. 65, 66^ and 67, taken from Hoyer and Udziela's paper, show 

 these relations clearly. The chief points in which the adult differs 

 from the larva are, first that the hearts are more deeply embedded in 

 the muscles, second that the T. lymph, long, lateralis pursues a more 

 zigzag course, and is not so clearly defined, and third that there tends 

 to be formed between each heart and the V. lateralis a short efferent 

 stem, so that the heart is further removed from the vein. 



Zacwilichowski (19 17) has studied the development of these 

 lateral hearts in Molge vulgaris (presumably Triton taeniatus\ and 

 found that they develop from the wall of the vein, and later become 

 secondarily associated with the lymphatic system. 



There remains yet the central lymph heart (ct.ly.h.) to be con- 

 sidered. Its location in the truncus arteriosus has already been 

 described (p. 1 90). To observe it the bulbus cordis must be severed 

 near the ventricle and turned over anteriorly — then, if the muscles 

 on the dorsal side of the truncus arteriosus be carefully removed, 

 the lymph heart is revealed. The lymph enters from the T. peri- 

 pharyngeus between the carotid and systemic arches and is dis- 

 charged, posterior to the pulmonary arch, into the proximal portion 

 of the lingual vein (V. pharyngea). Regurgitation at both entry and 

 exit is prevented by valves. Greil's figures are a little misleading in 

 that he shows the afferent vessels pointing directly forwards. Accord- 

 ing to Hoyer and Udziela they form a more oblique angle even in 

 the larva, while in the adult their direction is almost transverse. The 

 shape of the central lymph heart is roughly pyramidal, the base being 

 directed forwards, while the apex is continued posteriorly as a fine 

 vessel draining lymph from the bulbus cordis. The central lymph 

 heart really lies dorsal to the truncus arteriosus, but, during develop- 

 ment, it becomes enclosed by a strap-like band of cardiac muscle 

 from the bulbus cordis that grows completely round between the 

 right and left carotid arches and forms a continuous strip connecting 

 the dorsal and ventral sides of the truncus arteriosus. 



It is uncertain whether there is an intrinsic rhythm in the heart 

 itself or whether the contraction is brought about entirely by the 

 extrinsic muscles of its neighbourhood. 



