Animal studies have suggested that animals at rest for prolonged periods of time show decreased ability to break down fat as a result of decreased enzymatic activity of certain lipases.
He'll leave a gamey piece of goat in this brew for about five days, allowing natural enzymatic action to tenderize the meat, while the marinade keeps bad bacteria at bay.
The choice of purification methods and the source of the drug will determine the nature and amount of contaminants in the final medicine. (Nothing is ever 100% pure.) Moreover, protein folding, various kinds of enzymatic modifications and impurities inevitably introduce variation, sometimes with unexpected results.