On the Production of the First Sound of the Heart. 331 



illuminated surface. Having experimented with the extinction of 

 light at other parts of the retina, he finds that it obeys the same 

 law. Since a large and a small area having the same actual illumi- 

 nation appear to be of different brightness, an investigation was made 

 of the relative luminosities of the two, and it was found that the two 

 were connected by a very simple law. 



The reduction of the intensity of a coloured ray to extinguish 

 all colour was next measured with areas of different dimensions, 

 and it was shown that again the intensity of the reduced light was 

 connected with the size of the spot by a simple expression similar to 

 that of the extinction of all light, but the exponential coefficient 

 differed, indicating that light and colour were not connected together 

 in the manner which might be expected. 



The author then deals with the question of colour fields, and finds 

 that all colour fields are of the same form, the extent depending 

 solely on the illumination and the area of the surface the image of 

 which falls on the retina. He finds that there is a connection 

 between the intensity of the colour and the extent of the field which 

 can be expressed by a formula, as also can the connection between 

 the size of the spot of illuminated surface and the extent of field. 

 He gives the curves of illumination for equal colour fields, and the 

 curves of extent of field for every colour in the prismatic spectrum. 

 Finally he makes an investigation into the relative sensitiveness to 

 light of various points in the retina, and shows that there are 



iso-lumes " or fields of equal sensitiveness which appear to be of 

 the same form as the colour fields. 



He points out that there are difficulties in reconciling these 

 results with either the Young or Hering theory of colour vision, and 

 suggests a modification in the accepted theory of light and colour 

 which may explain the connection between the two. 



•" On the Mechanism by which the First Sound of the Heart is 

 Produced." By Sir Richard Quain, Bart., M.D., F.R.S. 

 Received April 29, — Read June 3, 1897. 



It is a well-recognised fact that the action of the heart is accom- 

 panied by the emission of certain sounds, which are described as the 

 first and second sounds of the heart. These soands, which were 

 observed soon after Laennec had discovered the use of the stethoscope, 

 have been compared to the sounds produced by the utterance of the 

 words lubb-diip. They have been studied with interest by the 

 physicist, the biologist, the pathologist, and the clinical physician, 

 by the latter especially, inasmuch as the changes produced by disease 

 in the character of these sounds become of material assistance in the 



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