RESUMEN
The data obtained in this work could be summarized as follows: 1. The LD 50 of tartar emetic was 49/kg, it produced a significant reduction of haemoglobin content and haematocrite value. It was the most toxic drug to the heart and lungs. Pharmacological studies showed that it produced direct depression on the isolated rabbits, heart, a perasympathomimetic effect manifested on isolated rabbits, intestine and blood pressure of anaesthetized dogs. 2. The LD 50 of astiban was 290 mg/kg. The results of subacute toxicity tests were similar to those obtained with tartar emetic but it was devoid of any toxic effect on heart. Pharmacological studies showed that it produced parasyupathomimetic effect on isolated rabbit's heart. 3. LD 50 of Hycanthone was 57 mg/ kg. No effect on the blood picture of rats was observed it was more toxic to the liver. It produced direct cardiac inhibition on the isolated rabbit's hearts, parasympathomimetic effect on the isolated rabbit's intestine and blood pressure of dog. 4. LD 50 of niridazole was 990 mg/ kg. The results of subacute toxicity tests were similar to those obtained with hycanthone. It is more toxic to brain it produced direct cardiac inhibition on the rabbit's heart and hypotension in dog