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animals became easy prey to secondary infections. The effects of DOT 
in experimental animals are cumulative! small single doses given re- 
peatedly lead to chronic poisoning* In a group of 10 rats eaoh weigh- 
ing about 80 grams, DDT fed at a level of 0*1 percent in the diet was 
uniformly fatal in from 18 to 80 days*. Generalized tremors were present 
throughout* At a level of 0*05 percent of DDT the animals survived 3 
months, though there was some impairment of growth* In the study on 
rabbits a mild degree of anemia was evidenced by a reduction of the 
hemoglobin level* White blood cell counts however, failed to indicate 
significam; deviations from the normal* The safe level in human foods 
cannot be over 10 p*p*m* "I, myself, would not risk more than 70 
milligrams, or 1 mg* per kilogram •"— Calvery (105 ) • 
Daily doses of oily solutions containing 10 percent of DDT were 
administered orally to dogs in the ratio of 100 mg* of the drug per 
kilogram of body weight until symptoms of intoxication appeared* In 
some cases slight symptoms were apparent after a few days, but the 
animals recovered promptly and spontaneously* It was only after new 
administrations of DDT that intense symptoms were observable* Spon- 
taneous recovery occurred 12 to 24 hours after treatment* From then 
on the susceptibility of the animals to the drug inoreased greatly* To 
verify the effect of calcium on the development of the symptoms of 
poisoning, these animals were given doses of 150 to 200 mg* of DDT per 
kilogram of body weight* Calcium gluconate (10 percent solution) was 
injected intravenously to investigate its curative and preventive effects* 
"The satisfactory results obtained by the use of calcium gluconate in 
prevention and treatment of dogs experimentally intoxicated by DDT 
suggest that the apparent neurologic symptoms observed are consequent 
to hypocalcemia, and not due to direct action of the DDT upon the 
central nervous system*" All but one of the six dogs used in these ex- 
periments was in apparently good physical condition a month after the 
experiments were ended*— Vaz et al* (361 ) * 
Beginning January 10, 1944, rats were kept on a diet containing 1 
part of DDT in 10,000 parts of foodstuff. On March 11, just 2 months 
later, they began to have convulsions* Two days later half the rats 
were restored to normal food with near disappearance of convulsions* 
However, both the withdrawn rats and those remaining on the DDT diet 
died within the next 2 days* In May 1944, the Bureau of Entomology and 
Plant Quarantine fenced 3/4 acre of grassland containing grasshopper 
egg masses about 60 miles from San Diego, Calif* When the hoppers were 
emerging, the area was fairly effectively du3ted at the rate of 40 pounds 
per acre with a 10-percent DDT dust* After 48 hours the California 
State Bureau of Chemistry was permitted to put 3 ewe sheep in the field* 
After 72 hours the sheep showed extreme neurologic symptoms, reminding 
one of dogs suffering from rabies* Nervous disorder in the sheep was 
characterized by tremors and especially by motion in the hind legs simi- 
lar to stringhalt in horses* Iheir necks seemed to be affected, as they 
