CHLORTHION SPRAYS at 0.5-percent concentration were tolerated by adult cattle.

The minimum toxic oral dose of Chlorthion for both dairy calves and adult cattle was between 50 and 100 mg./kg. Adult cattle were severely poisoned by 2 doses, each of 50 mg./ kg., given 48 hours apart.

BAYER COMPOUND 21/199 was toxic for young calves at 0.5-percent concentration in sprays.

Adult cattle were not poisoned by 0.5-percent sprays. One yearling Hereford heifer given 50 mg./kg. of compound 21/199 died of poisoning; a similar heifer given 25 mg./kg. was unaffected.

SYMPTOMS OF POISONING by organic phosphorus compounds studied in our experiments (parathion, EPN, malathion, Bayer L 13/59, Chlorthion, and Bayer 21 / 199) are so similar from compound to compound that we could find no real differences. The symptoms are those associated with interference in the activity of the enzyme that destroys esters of choline.

Poisoned animals generally first show excessive salivation. The flow is abundant, and the consistency of the saliva approaches that of water. The animal then usually encounters respiratory difficulty and breathes with the mouth open and with greatly exaggerated respiratory movements. As the respiratory effort increases, the animal walks stiff-legged and wanders about restlessly. Rippling spasms of all body muscles are present. Eventually exhaustion forces the animal to lie down. As death approaches, there are rasping sounds from the lungs and the animal grunts softly with each breath. Death appears to occur by respiratory failure. With the very high doses convulsions have been seen.

THE LESIONS found at necropsy in acute poisoning by cholinesterase-inhibiting insecticides are never outstanding and never sufficient to prove these compounds as the cause. In many cases the necropsy findings are entirely negative.

In cases that show lesions, there may be hemorrhages of varying sizes on the heart, lungs, stomach, or intestines. The lungs may be congested, edematous, and heavy, Frothy exudate is often present in the bronchi and trachea.

When the animal is affected over a long period, pneumonia may occur. In our experience several cases have suggested pneumonia by the symptoms, but the lungs were perfectly clear at necropsy.

ATROPINE is a specific antidote for poisoning by this group of compounds. It may be given by a veterinarian subcutaneously, intramuscularly, or intravenously.

In our studies of the treatment of poisoning of sheep and cattle, we have had remarkable success in using the intravenous and subcutaneous routes together, giving approximately one-fourth of the total dose intravenously and the remainder either subcutaneously or intramuscularly.

For poisoned cattle, at least 45 milligrams of atropine sulfate should be given for each 100 pounds of weight. Higher doses must be given if the animal has been severely poisoned.

An initial dose of 1 milligram for each pound of weight should be given to sheep.

Regardless of the initial dose given, additional doses must be given in most cases to keep the animal under the influence of the atropine, usually for at least 24 hours.

The specific treatment must be followed by removal of the remaining insecticide by washing or purging or other indicated methods.

R. D. RADELEFF became veterinarian in charge of the Kerrville, Tex., laboratory of the Animal Disease and Parasite Research Branch in 1949. He is a graduate of Schreiner Institute and of the Agricultural and Mechanical College of Texas.

G. T. WOODARD was made the assistant veterinarian of the Kerrville laboratory in 1952. He is a graduate of the Agricultural and Mechanical College of Texas. He has assisted in the Kerrville studies since 1952.

R. C. BUSHLAND became entomologist in charge of the Kerrville laboratory of the Entomology Research Branch in 1951. He is a graduate of South Dakota State College and received his doctorate from Kansas State College. Most of his work, since he joined the Department of Agriculture in 1935, has been with insecticides.