Is it because some of the drugs which affect the stomach are hot and others cold, so that some of them, owing to their heat, as soon as they reach the upper part of the stomach are carried thence to the upper region of the body, melting in particular anything there which is most alien to them and least substantial; and if the drug be powerful or has been administered in a dose stronger than nature can withstand, it carries these liquefactions and any excretions that there may be down into the upper part of the stomach, and by its heat stirring up the breath, which it engenders in great quantity, checks their progress and causes vomiting?