38 Dr. W. Stirling. On the Lung of the Newt. [Apr. 7, 



lium. Tlie ciliated epithelium is directly continuous with that lining 

 the short trachea. 



The nerves of the lung are very numerous and are branches of the 

 vagus. They enter the lung in three or four main strands at its base. 

 These strands are of unequal thickness, i.e., a varying number of 

 nerve-fibres enters into their composition. At once they proceed 

 towards the pulmonary vein, which they follow very closely in their 

 distribution. They form a plexus along the course of the vein, which 

 is readily revealed with the aid of gold chloride. Only a few non- 

 medullated nerve-fibres pass on to the pulmonary artery. The nerve- 

 strands lie outside the muscular coat, and as they pass onwards in the 

 pulmonary walls they give off branches right and left. A large 

 number of multipolar nerve-cells exists in the course of the nerve- 

 strands, and they are especially numerous where a branch is given off. 

 More than twenty medullated nerve-fibres and a considerably larger 

 number of non-medullated fibres enter the lung. The nerve-strands 

 in their course along the pulmonary vein lie in spaces lined by 

 squamous epithelium. 



The branches of the nerve-strands lie outside the muscular coat. 

 The axial cylinders split up into fibrils, many of which divide dicho- 

 tomously, and afterwards unite to form a wide meshed primary nerve 

 plexus external to the muscular coat. From this branches are given 

 off which form a much finer secondary plexus, which gives off very 

 fine branches which run towards the muscular fibres in which they 

 seem to terminate. It cannot, however, be maintained that all the 

 nerve-fibres which enter the lung terminate in the muscular coat. 

 The majority of the non-medullated nerve-fibres distributed along the 

 course of the pulmonary artery seem destined for the muscular tissue 

 in its walls. The author has found a, plexus of .nerve-fibres in the 

 adventitia and another in the muscular coat of the pulmonary artery. 

 Some of the nerve-fibres must, undoubtedly, have other relations than 

 those indicated above. 



The author points out that, as the lungs are developed from the 

 alimentary canal, it is to be expected that structures, the exact 

 homologues and representatives of those occurring in the wall of the 

 alimentary canal, may be expected to occur in the lung. He suggests 

 therefore, that the non-striped muscle in the wall of the lung of 

 the newt, and the tracheal and bronchial muscles in the mammalian 

 lung, are the representatives of one or more of the muscular tissues 

 of the alimentary canal ; and, as each of these muscular tissues has a 

 nerve plexus in relation with it, a similar condition may be expected 

 to occur in the lung. The plexus in the wall of the lung is com- 

 parable to Auerbach's or Meissner's plexus, or perhaps to both. 



