215 



annexed. From these and other details given in the paper, the author 

 concludes that the apparent direction of the eyes to or from the 

 spectator, depends upon the balance of two circumstances combined 

 in the same representation ; namely, 1st, the general position of the 

 face presented to the spectator ; 2nd, the turn of the eyes from that 

 position ; and thence proceeds to examine why, if the eyes of a por- 

 trait look at the spectator placed in front of the picture, they appear 

 to follow him in every other direction. When two objects are seen 

 on the ground at different distances from us iu the same direction, 

 one appears and must be represented exactly above the other, so that 

 a vertical plane from the eye would pass through them ; and since 

 such a line will be seen upright, however far we remove to one side, 

 it follows that the same objects still seem to be in a line with us ex- 

 actly as in the front view, seeming as we move to turn from their 

 first direction. 



In portraits the permanence of direction, with reference to the 

 spectator, and corresponding change of its apparent position in space 

 when he moves to either side, depends upon the same principles. 

 The nose drawn in front, with its central line upright, continues di- 

 rected to the spectator, though viewed obliquely ; or if the right side 

 of the nose is represented, it must appear directed to the right of the 

 spectator in all situations ; so that eyes that turn in a due degree 

 from that direction towards the spectator, so as to look at him when 

 viewed in front, will continue to do so when viewed obliquely. 



Further Particulars of a Case of Pneumato-thorax. By John Davy, 

 M.D.F.R.S. Read March 4, 1824. [Phil. Trans, 1824, p. 257.] 



About a month after the operation described in Dr. Davy's former 

 paper, when the patient appeared to be doing well, symptoms of 

 hydrothorax came on, and fluid again collected in the left side of the 

 chest. A second operation therefore was performed, and fourteen 

 ounces of fluid discharged through a perforation in the fifth rib. 

 During the six. following weeks not less than twenty pints of fluid 

 ran off through the opening ; at first it was transparent, but became 

 gradually more and more purulent, and was mixed with air com- 

 posed of oxygen, azote and carbonic acid, in various proportions. The 

 patient's health improved at first progressively, but in about six weeks 

 after the operation he became worse, and expired suddenly. On ex- 

 amination after death, about six ounces of pus were found in the left 

 pleura. The right pleura was healthy, but tubercles and vomicse 

 were found in the right lung ; the left lung wfis much condensed, 

 and communicated by two small openings with the pleura. Dr. Davy 

 refers the origin of the disease in this case to a communication be- 

 tween the aspera arteria and cavity of the pleura, established by the 

 rupture of a superficial bronchial tube, and the membrane covering 

 it ; and concludes the paper with some remarks upon the fluctuating 

 composition of the air from the chest, which he attributes not to the 

 varying quantity of atmospheric air, admitted through the perfora- 



