Charak Samhita
जङ्गमं स्यादधोभागमूर्ध्वभागं तु मूलजम् । तस्माद्दंष्ट्राविषं मौलं हन्ति मौलं च दंष्ट्रजम् ॥१७॥
The animal poison moves downwards whereas the vegetable poison moves upwards in the alimentary canal. Therefore, the animal poison cures poisoning by vegetable-poison and the poisoning caused by animal-poison is cured by vegetable poison.
english translation
jaGgamaM syAdadhobhAgamUrdhvabhAgaM tu mUlajam । tasmAddaMSTrAviSaM maulaM hanti maulaM ca daMSTrajam ॥17॥
hk transliteration by Sanscript