Pathologic Changes Produced by Subcutaneous Injection of Rattlesnake (Crotalus) Venom into Macaca mulatta Monkeys. ∗

Reports of the gross and microscopic lesions in fatal cases of rattlesnake poisoning are rare. Knowledge of the pathologic changes is based mainly upon findings in experimental animals, 1 These changes have been described in detail in dogs.^2,3 Taube and Essex 3 administered large doses of venom (crotalin) intravenously and produced widespread hemorrhagic lesions throughout the body. In nature, however, the venom is usually injected subcutaneously. It is our purpose to report the lesions produced by the subcutaneous injection of a lethal dose of crotalin into the Macaca mulatta 4 monkey.

Nine young Macaca mulatta monkeys were given rattlesnake (Crotalus atrox) venom into the subcutaneous tissues of the lumbar region. The dose, given as a 1% solution in saline, corresponded to 7 to 10 mg of the dried venom per kilo of body weight.

For several hours after injection the animals behaved about as usual, but later became weak, lethargic, and refused to eat. The lethargy and weakness increased in severity until death occurred at an average of 36.5 hr after injection.

Postmortem examination revealed in the subcutaneous tissues an intense hemorrhagic edema which involved about 50% of the body area. It extended from the mid-thoracic region to the buttocks and groin, and, in several cases, down as far as the knees. At the advancing edges of the lesion there was marked edema but no hemorrhage. The regional lymph nodes in the groin, and to a less extent the iliac, pre-aortic, mediastinal and axillary nodes, were swollen and red. In the heart there were small subendocardial hemorrhages in the left ventricle in the region of the interventricular septum near the aortic ring. This occurred in 6 of the 9 animals. Other lesions were not constant and consisted in one animal of small sub-pleural hemorrhages, and small sub-capsular hemorrhages of the liver, and in 2 others of petechial hemorrhages into the mucosa of the cecum. The lungs and abdominal viscera were pale and dry.