"I do have some experience in some matters similar to this," he said thoughtfully as he followed Alex's instructions and, after a bit of trying, managed to begin the process of milking this first snake. "We knew of herbs that were medicinal in small doses but dangerous in larger ones. We knew that if we exposed ourselves to them gradually, we would eventually become immune. Much like one of our horses who enjoyed hunting snakes. The beast was dealt many a glancing blow by the creatures until he no longer feared their bite; they had no effect upon him." Immunity granted by exposure.

And the thought narrowed his eyes. Made him consider. "I believe I may know of something else similar. The practice of exposing people to small amounts of disease..."

A snippet of what the Apple had shown him but he hadn't quite been able to grasp until now. His mind had just been too old to make the connection.