THE SENSES 



831 



be made by the colour-blind without necessarily leading 

 them to suspect that there is anything abnormal in their 

 vision. Thus, to quote the words of a distinguished writer 

 on this subject, himself a sufferer from the deficiency: 

 ' A naval officer purchases red breeches to match his blue 

 uniform ; a tailor repairs a black article of dress with 

 crimson cloth ; a painter colours trees red, the sky pink, 

 and human cheeks blue.' The shoemaker, Harris, the dis- 



FIG. 319. PERIMETRIC CHART OF RIGHT EYE. 



Obtained with the perimeter shown in Fig. 318. The numbers represent degrees 

 of the visual field measured on the graduated arc of the perimeter. 



coverer of colour-blindness, picked up a stocking, and was 

 surprised to hear other people describe it as a red stocking ; 

 it seemed to him only a stocking. The celebrated Dalton 

 was twenty-six years of age before he knew that he was 

 colour-blind. He matched samples of red, pink, orange, 

 and brown silk with green of different shades ; blue both 

 with pink and with violet ; lilac with grey. 



