Gangadhar commentary on charak samhita says the tendency of animate poisons is to move upwards in the body. :
जङ्गमंस्याद् उर्ध्वभागं ( jaṅgamaṁsyād urdhvabhāgaṁ )Meaning: Gangadhar commentary on charak samhita says the tendency of animate poisons is to move upwards in the body.
