1 86 THE SALAMANDER 



occurred. He thought that the acute angle at which the ductus 

 BotalU meets the systemic arch would cause the former to be 

 closed when the pressure in the latter rose beyond a certain mini- 

 mum, and thus an admixture of blood in the two arches would be 

 prevented. Suchard (1902) continued and extended Brucke's in- 

 vestigations. He thought that separation did actually occur but 

 that it was only partial. He experimented by injecting a coloured 

 fluid into the ventricle of an anaesthetized animal and found that it 

 first entered the pulmonary arch, and therefore concluded that the 

 first blood to leave the ventricle at the commencement of the systole 

 would likewise enter the pulmonary arch. More recently, Nakano 

 (19 1 3) and Haberlandt (19 16) have conducted physiological experi- 

 ments on the heart of the Salamander, but their results lie rather out- 

 side the scope of the present work. The experiments were mainly 

 of an electrical nature and were designed to elucidate the nature and 

 sources of the nerve stimuli controlling the heart movements. Ziil- 

 lich's contribution to the physiological aspect has already been 

 mentioned and will be referred to again on p. 191. 



2. Description (PI. XIII, figs. 59 and 60). 



The present investigation was commenced before Ziillich's paper 

 appeared, and it was decided to reconstruct the anterior end of the 

 ventricle, bulbus cordis, and truncus arteriosus by the wax-plate 

 method in order to elucidate the details of their structure. The fol- 

 lowing description is based on a study of this model and of the 

 sections from which it was built, as well as on the dissection of other 

 specimens. 



External Features. 



The heart of the Salamander is relatively much smaller than that 

 of the Frog, while the ventricle (ven.) is shorter and has a more 

 rounded apex, which is displaced a little to the right of the middle 

 line. As seen in the ordinary course of dissection in a fresh or pre- 

 served specimen, the anterior face of the ventricle, instead of lying 

 in a transverse plane as in Rana, is inclined obliquely to the left, 

 and the auriculo-ventricular opening, instead of being at about the 

 same transverse level as the opening of the bulbus cordis, is posterior 

 to it, while at the same time both auricles are displaced to the left. 

 The bulbus cordis'^ (b.c.) arises from the right antero-ventral angle of 

 the ventricle and is inclined slightly to the left. It expands distally, 

 where it merges into a short, thick truncus arteriosus (t.a.), from which 

 ' Often incorrectly described as the truncus arteriosus, see p. 1 89. 



