On the other hand, had the residue of 2.2 p.p.m. been reported, it would have lacked 
impressiveness and a diagnosis of some other condition may have been made, erroneously 
clearing the insecticide. 
We have, in the past, suggested that chemical analyses be performed on hair or 
ingesta and that large quantities present would indicate poisoning. That has been altered 
by several complications. We now know, froma study with lindane, that low residues on 
hair may exist in poisoning. We also are ata loss to specify the quantity of compound in 
ingesta which will or would result in poisoning. Bioassays of hair or gastrointestinal 
content would yield grossly misleading results. 
Organic phosphorus compounds may or may not leave detectable residues, according 
to the material. The use of chemical analyses with these materials is as confusing as it 
is with chlorinated hydrocarbons, 
We emphasize that chemical analyses usually serve to confuse rather than inform 
when we attempt to use them as an aid in diagnosis. 
Problems in Sampling 
There would be no need toemphasize this point, but samples continue to be shipped in 
such a manner as to either confuse the chemist or make analysis impossible. 
The need for fresh tissue in quantities as near 500 gms., if the organ permits, free 
of preservatives and contaminants and properly refrigerated cannot be over emphasized. 
If fresh tissue is not always available, one should not expect the chemist in turn to 
be as good in his analysis. 
Samples of tissues weighing onlyafewgramsare rarely enough for a single analysis, 
much less for duplicates or for analyses for more than one substance, 
Preservatives should never be used, because they may easily mask the reactions de- 
sired. 
Freezing is preferred in all cases. Shipment should be in liberal quantities of dry 
ice and by air or messenger. Most chemists prefer polyethylene bags as sample con- 
tainers. Cartons, boxes, and bottles may contain waxes or finishes which confuse the 
analysis. 
Otherwise satisfactory samples are often ruined by the presence of antiseptics or 
soaps from gloves and hands or insecticide from hair or dirt blown or carried into the 
sample. 
Because the final reaction in the analysis may be for an entirely different molecule-- 
for example benzene in the lindane analysis or sodium chloride for some chlorinated 
hydrocarbons, the presence of all extraneous chemicals must be avoided. 
The chemist should be informed of the insecticide suspected, but here another dif- 
ficulty is encountered. Animals fed treated forage or feed will show some residue in their 
fat in almost all cases. Therefore, finding a residue is not conclusive evidence. The 
person submitting the sample should keep his mind open to all other chemicals, including 
sprays and dips, to which the animal may have been exposed. 
Unless the tissues are analyzed for all possible substances, the finding of one simply 
leads to erroneous conclusions. 
Above all, the presence of a residue of insecticide must never be taken to indicate 
anything more than exposure to that material. Presence of a residue must never be taken 
as a diagnosis of poisoning. 
iMSyN 
