That's a really good question. Like human saliva, snake saliva includes enzymes that begin breaking down the prey's body as it travels towards the intestines. But I don't know how fast it works and how 'strong' it is... and since prey is pretty much always dead when it goes down, I doubt anybody really knows the effects of this on a live human. I assume living tissue breaks down differently than in a dead person without circulation. Short answer... if you want him to survive this, keep his clothes on.