METHODS OF STUDYING VISION IN ANIMALS 



2L 



It is held firmly in position by two screws through diagonally 

 opposite corners of the metal frame p. At any time by loosening 

 the screws (v. fig. 3) the experimenter may readily remove a 

 plate and replace it by another with an opening of different 



,<^ / 



Figure 3 — Construction drawings for stimulus adapter. Dimensions in milli- 

 meters. Front vieiv. Back view; p, brass plate framing the aperture in alumi- 

 num plate y; u, head of one of the two screws which serves to hold opal glass 

 plate firmly against standard brass stimulus plate (the other screw is in the 

 corner diagonally opposite) ; v, one of the two screws which serves to hold 

 standard stimulus plate in position (the other is in the corner diagonally oppo- 

 site) ; w, screws attaching hard rubber ring to p ; a-b, and b-c indicating sec- 

 tions. Section u-b; d, d', metal straps with ral^beted edge for aluminum plate 

 y; e, strap connecting d and d'; f, steel spring on h, bolt tying d to z; g, brass 

 collar for screw, i, which attaches brass track, k, to d; m, n, o, t, parts of brass 

 roller which enables y to move on track; p, brass plate framing aperture in y; 

 r, hard rubber ring about aperture; w, screw attaching r to p; s, standard 

 l)rass stimulus plate. Section b-c; I, plate of flashed opal glass. 



size or form. The set of standard plates is fully described in 

 connection with table 3, p. 23. Between the frame p, and the 

 standard plate, s, is inserted a piece of opal flashed glass, 1.. 



