Snakes consisting Poison Apparatus by the contraction of digastric muscles in Poison Apparatus in snake the mouth is opened. Then the lower jaw moves forward. The sphenopterygoid muscles contract which results in the forward movement of pterygoid which brings rotation of maxilla, results the fang is raised and becomes directed forward.

 

 

The contraction of the digastric muscle will squeeze of poison gland. This makes the poison to come out of the poison gland and flows into the enemies body.