On these lines, then, of the improved understanding of first principles, I will now proceed to develop the teachings of Medical Jurisprudence. The first principle that I will lay down for explanation is, that a man is not to be held responsible for all his acts, but only for those which he does of his own free will, which, therefore, it is in his power to do or not to do. These are called _human_ acts, because they proceed from a distinctively human power. A brute animal cannot perform such acts; it can only do under given circumstances what its impulses prompt it to do; or, when it experiences various impulses in different directions, it can only follow its strongest impulse; as when a dog, rushing up to attack a man, turns and runs away before his uplifted stick. When a bird sings, it cannot help singing; but a man may sing or not sing at his choice; his singing is a human act. When, however, under the impulse of violent pain, a person happens involuntarily to sigh or groan or even shriek, this indeed is the act of a man, but, inasmuch as it is physically uncontrollable, it is not a human act. So whatever a patient may do while under the influence of chloroform is not a human act, and he is not morally responsible for it. His conduct under the circumstances may denote a brave or a cowardly disposition, or it may indicate habits of self-command or the absence of them. His prayers or curses while thus unconscious are no doubt the effects of acquired virtues or vices; yet, in as far as his will has no share in the present acts, they are not free or human acts. He deserves praise or blame for his former acts, by which he acquired such habits, but not for his unconscious acts as such. From this principle it follows that a physician is not responsible to God or man for such evil consequences of his prescriptions or surgical operations as are entirely beyond his will and therefore independent of his control. If, however, his mistakes arise from his ignorance or want of skill, he is blamable in as far as he is the wilful cause of such ignorance; he should have known better; or, not knowing better, he should not have undertaken the case for which he knew he was not qualified. But it often happens that the best informed and most skilful practitioner, even when acting with his utmost care, causes real harm to his patients; he is the accidental, not the wilful, cause of that harm, and therefore he is free from all responsibility in the matter.