Lewis and his associates1 of the Wistar Institute, University of Pennsylvania, showed that DDT is nontoxic for tissue cultures. Normal growth took place with cells of the heart, liver, kidney, stomach, intestine, skeletal muscle, brain and spinal cord of chick embryos or of 1 day rats, even in the presence of a saturated solution of DDT. The conclusion seemed evident that the site of action of DDT must be somewhere in the complex integration of the intact animal. This was in line with a previous report by Yeager and Munson2 of the U. S. Department of Agriculture, who made a pharmacologic analysis of the action of DDT when injected into the roach (Periplaneta americana).
In the intact roach the symptoms of DDT toxicity are increased activity with the appearance and persistence of contractions and tremors in the appendages, erratic behavior and loss of equilibrium. In a typical experiment,