FIELDS W, X, and Y 

 Columns 68; 69 and 

 70; and 71 



When data from tests indicate that the minimum dose needed to affect 100% of individuals has 

 been determined, the Grid can be used to determine the Field Y code evaluation. (This dose being 

 minimum to affect 100% of the individuals tested is evidenced by the laboratory's having administered, 

 of a series of dose levels, at least one dose level which affects less than 100% of individuals. ) 



4. When plotting data on the Grid, particular attention must be given to the selection of the proper 

 point on the abscissa (the horizontal scale of the Grid). On this scale, each major dividing line marks 

 off a linear section of the scale, there being a total of nine such equal sections of the scale. (Each 

 section can be considered as projecting two-dimensionally as a column across the Grid area.) Each of 

 the nine sections represents one range of a scale of Field M, N, P, or U. For example, the section of 

 the abscissa from the left edge of the Grid to the first of the nine heavier lines dividing the total 

 abscissa represents the first range of any scale of Field M, N, P, or U (e. g. , 0. 081-0. 243 mg [Scale 2 

 of Field N], or <6 hours [Scale 7 of Field P]). The next equal section of the abscissa scale of the Grid 

 represents the second range of any scale of Field M, N, P, or U, and so on. 



Within any of these nine sections of the abscissa of the Grid, the coder should attempt to 

 envision the distribution of values (logarithmic in progression) represented by the particular ranges of 

 dose and time values and thereby select the most appropriate point on this section, rather than place 

 the coordinate arbitrarily anywhere within the section. For example, 0. 05 mg/kg (Range 2 of Scale 4 

 of Field N) would be a point just to the right of the first major vertical dividing line of the Grid, 0. 18 

 mg/kg (also Range 2 of Scale 4 of Field N) would be just to the left of the second major dividing line, 

 and 0. 08 mg/kg would be nearly mid-way between the first and second of the dividing lines. 



5. In the case of certain biological fields and certain specific responses, even the most effective 

 or "potent" compound or compounds discovered to cause the response produce the specific response 

 only when administered in relatively large amounts. For example, if the most potent compound known 

 for a given response produces the response only when administered in quantities of 1. 5 grams or 30-40 

 lbs/acre, this compound will be evaluated by Criterion 51, 52, or 53 as being "low in effectiveness" 

 (Grid area and Field Y Code Symbol 1 or, at most, 3), regardless of the percentage of individuals (of 



a group of individuals) affected by this quantity. Unknown compounds tested for that same specific 

 action can be expected to fall in the same general category so that the Grid provides no evaluation 

 distinction between those compounds; in other words, all compounds (even the most effective) tested 

 for that particular action would be evaluated as being low in effectiveness. The same difficulty may 

 occur at the other end of the Grid in the case of other biological responses which occur typically with 

 very small quantities of test compound so that nearly all compounds tested for such a response will 

 fall in area 9 (or 7) of the Grid and be evaluated as being "high in effectiveness". 



Actually, the evaluations afforded by the criteria using the Log-Probit Grid are not intended to 

 be evaluations of test compounds' abilities to produce each specific response. (This could only be 

 done if each specific response of Field T-2 were accompanied with special dose ranges typical of 

 that response and if this dose range were then used on the Grid rather than the single dose range now 

 fixed to the Grid. ) The general aim of the evaluation field has been to express, whenever possible, 

 the potency of the test compound for producing biological responses in general; if a particular response 

 occurs in most individuals only with a large quantity of test compound, the potency of the compound 

 for that particular action should be regarded as being "low" even if it is the compound with highest 

 potency known for that action; if a particular response occurs in most individuals with a very small 

 quantity of test compound, the potency of the compound for that particular action should be regarded 

 as being "high", even if most compounds causing the response cause it typically with small doses. 



This is the purpose of the single fixed Log-Probit Grid. If, in retrieving data evaluated by the 

 Grid, it is discovered that all evaluations for a particular response, or for a particular type of response, 

 appear to be low evaluations (Symbols 1 or 3) or high evaluations (9 or 7), the interpretation should 

 be that the data indicate the response (or the use for which the compound is tested) is of a type for 

 which only large quantities of test compound (evaluation Symbols 1 or 3) are practicable or a type for 

 which only small quantities of test compound (evaluation Symbols 7 and 9) are practicable. The inter- 

 pretation should not be that, of all the compounds which are found to be evaluated with Symbols 1 or 3, 

 none are practicable for the specific activity (Field T-2). 



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