. The Dental cosmos. Holzknecht radiometer with both the indexand measuring pastils in position. reading is made. Fig. T shows the slid-ing arm in a lower position. Here theindex pastil is under the dark or coloredportion of the colored celluloid band,while the measuring pastil, which hasnot been exposed to the ray. and there-fore has not changed in color, is underthe colorless piece of celluloid. Theillustration shows a distinct difference inthe shade of the two half pastils. Itwill be remembered that, when this slid-ing arm was in its original position(Fig. 6), both pastils were under color-
. The Dental cosmos. Holzknecht radiometer with both the indexand measuring pastils in position. reading is made. Fig. T shows the slid-ing arm in a lower position. Here theindex pastil is under the dark or coloredportion of the colored celluloid band,while the measuring pastil, which hasnot been exposed to the ray. and there-fore has not changed in color, is underthe colorless piece of celluloid. Theillustration shows a distinct difference inthe shade of the two half pastils. Itwill be remembered that, when this slid-ing arm was in its original position(Fig. 6), both pastils were under color- 40 NIK DKXTAL COSMOS. less celluloid, and therefore at zero theyaccurately matched in shade. Now, how-ever, they do riot match, but if the meas-uring pastil had been exposed to the raysufficiently to have made it match theindex pastil, as demonstrated in Fig. 7,the reading would he 2IT units (at h). Fig. Holzknecht radiometer with sliding arm atlower level. PRACTICAL APPLICATION OF HOLZKNECHTUNITS IN RADIOGRAPHY. Holzknecht units have the followingsignificance: One unit is one-third thequantity of ray necessary to producean erythematous reaction of the skinof the face of a middle-aged order to administer the maximumamount of ray without reaction, thefollowing units may be applied: Tomiddle-aged adults—Face 2H, scalp andjoints 3H, body 4H; to children—1H,2H, and 3H, respectively; to aged indi-viduals—3H, 4H, and 5H, amount can be applied at one sittingor divided into multiple exposures. But no more than these quantities must beadministered in the course of four weeks. The value of these units will vary ac-cording to the quality of ray figures above given appertain to aquality not lower than a No. 6 B. If ahigher quality is employed, the dose maybe increased, while, conversely, if thequality is softer, the dose must be dimin-ished. The qualit
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Keywords: ., bookcentury1900, bookdecade1910, bookiddent, booksubjectdentistry
