Ashtangahridayasamhita 9

9

koṣṭhaḥ krūro mṛdur madhyo madhyaḥ syāt taiḥ samair api |
śukrārtava-sthair janmādau viṣeṇeva viṣa-krimeḥ || 9 ||

The alimentary tract is hard, soft, or moderate; it is also moderate when they are balanced.
By them residing in the semen and ovum at the beginning of conception, like poison in a poison-worm, || 9