NO. II BODY RADIATION ALDRICH II 



r-r., ^- deflection with a filter interposed • r ^, 



Ihe ratio: — ■. ■, — ^ is a measure of the 



deflection without the filter 



direct transmission of the filter, plus a small quantity dift'usely trans- 

 mitted. Tests of the transparency of various screens were made. 

 These are summarized in Table 3. 



Table 3. 



Transiiiissio)i of various siihsfances. Temperature of source hetivccn 

 7^° and 170° C. 



Material Thickness % Transmitted 



Rock-salt 6.0 mm 85. 



Fluorite 5.5 " 44- 



Mica 03 " 50- 



Tissue paper 03 " About 45. 



Blotting paper 4 " Negligible. 



Hard rubber 13 "• Very small. 



Rubber dam 17 " Less than 10. 



Lampblack One coat, painted on 6 (partly due to pin holes) 



rock-salt. of rays transmitted by 



R. S. 

 Lampblack Two coats, painted at Less than h% of R. S. rays. 



right angles, on R. S. 

 Camphor smoke ....Smoked on R. S. plate. 20% of rays transmitted by 



so thick a lamp filament R. S. plate. 



is invisible through it. 

 Camphor smoke ....Very thick coat, flaking 6'y'c of R. S. rays. 



off. 

 Skin, freshly removed . .About 2 mm Negligible. 



Through the interest of a surgeon in a local hospital, a piece of 

 human skin was obtained immediately after removal from the body. 

 Its transmissibility was measured before it had materially lost its 

 moisture. The piece obtained was about 2 mm. in thickness, with some 

 fatty tissue adhering to it. When inserted as a screen in the arrange- 

 ment described above, its transmissibility was found to be wholly 

 negligible. Bazett and McGlone in a paper entitled " Temperature 

 gradients in the tissues in man" ( Amer. Journ. Physiol., vol. 82, 

 no. 2, p. 415, 1927) have shown that in general an increase of 1° above 

 surface temperature is found at a depth of something over 3 mm. 

 below the skin. Forsythe and Christison (General Electric Rev., 

 vol. 34, no. 7, p. 440. 1931) and others have pointed out that flesh, 

 since it consists largely of water, would be practically opaque to the 

 longer wave lengths, just as water is. It seems evident then that the 

 higher melikeron skin-temperature values are not due to the instru- 

 ment receiving radiation from deeper and warmer layers beneath the 

 surface. 



