ON ANTHROPOMETRIC INVESTIGATION IN THE BRITISH ISLES. 369 



colour-blindness, though it may fail to detect degrees of weakness of 

 colour- vision. 



The three test wools of the Holmgren set should be given each 

 separately to the subject, and he should be asked to choose the ten 

 other skeins most nearly resembling the test skein, and to lay them out 

 on the table in order of resemblance. Any naming of the colours should 

 be avoided until the subject has completed his selection, when he may, 

 with advantage, be questioned as to the names he would apply to the 

 test- wools. If the subject chooses wools of distinctly unlike colour- 

 tone, but of similar low saturation, it should be explained to him that 

 differences and resemblances of shade and of saturation are to be 

 neglected and those of colour-tone only regarded. Any grouping of 

 distinctly green tones with red, or of red with green, if not readily 

 rectified, must be taken as evidence of red-green blindness. Any 

 hesitation in distinguishing between red and green tones should lead to 

 a more searching examination. From this point of view it is important 

 to observe what wools the subject picks up and rejects, as well as those 

 which he finally selects. 



If time permits, each eye should be separately tested. 



The modified tintometer (designed by Mr. Lovibond for colour- vision 

 testing), in which the place of the coloured wools is taken by slips of 

 coloured glass presented against a white background, may be used in 

 place of the wools, but a larger series of glasses of lower saturation than 

 that at present supplied with the instrument would be required. Special 

 attention should be paid to the matches made with red and gi'een glasses 

 of low saturation. A red glass of low saturation should be placed in the 

 topmost space of the one vertical row and a green glass of low saturation 

 in the topmost space of the other vertical row as ' test-glasses ' ; the 

 remaining spaces may then be filled with glasses of various tones and 

 degrees of saturation, and the subject directed to resort them, placing 

 them beneath the ' t-^ st-glasses ' in the order of their resemblance to the 

 test-surfaces. 



This test may with advantage be made, first, with the apparatus at a 

 distance of 5 metres from the eye of the subject and then repeated at a 

 distance of 30 to 50 centimetres. 



TESTS OF HEARING. 

 Auditory Acuity, 



To be measured in tei-ms of the distance (number of metres) at which 

 the stroke of Pollitzer's 'Hor-messer ' can just be heard. 



The subject must be seated in a large, quiet room, or, better, in tlie 

 midst of an open space at some distance from all solid objects. The 

 Subject's eyes being closed and bandaged and the left ear stopped with the 

 finger, the instrument must be sounded at irregular intervals of two or 

 more seconds in a series of positions in the straight line passing from ear 

 to ear, first at 1 metre from the right car and then at positions succes- 

 sively 1 metre more distant from the ear. The subject is instructed to 

 say 'Now' each time he hears the stroke. When the subject fails to 

 respond to a stroke it must be repeated five or more times in the same 

 position. The series must be continued until a position is reached at 

 which the subject fails to respond more frequently than he succeeds. 



1008. n D 



