1881.] Dr. W. Stirling. On the Lung of the Newt. 37 



April 7, 1881. 



THE PRESIDENT in the Chair. 



The Presents received were laid on the tableland thanks ordered for 

 them. 



The following Papers were read : — 



I. " On the Minute Structure of the Lung of the Newt with 

 especial reference to its Nervous Apparatus." By William 

 Stirling, M.D., Sc.D., Regius Professor of the Institutes of 

 Medicine (Physiology) in the University of Aberdeen. 

 Communicated by Professor Huxley, Sec. R.S. Received 

 March 19, 1881. 



(Abstract.) 



The lungs of the newt and triton are essentially simple sacs without 

 any septa projecting into their interior, so that they are remarkably 

 well suited for microscopic examination. They are covered externally 

 by a layer of endothelium, but there are no stomata to be found 

 between the endothelial cells. Under this is a small quantity of 

 areolar tissue containing a plexus of yellow elastic fibres, with the 

 long axis of the meshes arranged in the long axis of the lung-sac. 

 Under this is a layer of non-striped muscular fibres, which forms a 

 complete investment for the lung. These muscular fibres are disposed 

 circularly. They present the same structure as similar cells in the 

 mesentery of the newt. Each cell contains an intra-nuclear and intra- 

 cellular plexus of fibrils. 



The arrangement and distribution of the blood-vessels is then 

 described. The pulmonary artery runs along one sid.e of the lung and 

 the pulmonary vein runs on the opposite side. The trunk of the 

 pulmonary vein lies quite superficially, i.e., next the peritoneal surface. 

 It is covered only by the serous investment of the lung, so that it lies 

 superficial to, i.e., outside, the muscular layer. The pulmonary artery 

 lies deeper, below the muscular coat. The capillaries are then 

 described. No capillaries exist internal to the line of distribution of 

 the pulmonary vein, but capillaries are found over, i.e., internal to, 

 the line of distribution of the pulmonary artery. The epithelium is 

 then described. Ciliated epithelium is found along the course of the 

 pulmonary vein and at the origin of its chief branches,, but the other 

 parts of the lung are covered by a single layer of squamous epithe- 



