But in reality, over and above this possession of our souls by others of our own species, the will of the lower animals often enters into our bodies and possesses them, making us do as they will, and not as we will; as, for example, when people try to drive pigs, or are run away with by a restive horse, or are attacked by a savage animal which masters them. It is absurd to say that a person is a single “ego” when he is in the clutches of a lion. Even when we are alone, and uninfluenced by other people except in so far as we remember their wishes, we yet generally conform to the usages which the current feeling of our peers has taught us to respect; their will having so mastered our original nature, that, do what we may, we can never again separate ourselves and dwell in the isolation of our own single personality. And even though we succeeded in this, and made a clean sweep of every mental influence which had ever been brought to bear upon us, and though at the same time we were alone in some desert where there was neither beast nor bird to attract our attention or in any way influence our action, yet we could not escape the parasites which abound within us; whose action, as every medical man well knows, is often such as to drive men to the commission of grave crimes, or to throw them into convulsions, make lunatics of them, kill them—when but for the existence and course of conduct pursued by these parasites they would have done no wrong to any man. These parasites—are they part of us or no? Some are plainly not so in any strict sense of the word, yet their action may, in cases which it is unnecessary to detail, affect us so powerfully that we are irresistibly impelled to act in such or such a manner; and yet we are as wholly unconscious of any impulse outside of our own “ego” as though they were part of ourselves; others again are essential to our very existence, as the corpuscles of the blood, which the best authorities concur in supposing to be composed of an infinite number of living souls, on whose welfare the healthy condition of our blood, and hence of our whole bodies, depends. We breathe that they may breathe, not that we may do so; we only care about oxygen in so far as the infinitely small beings which course up and down in our veins care about it: the whole arrangement and mechanism of our lungs may be our doing, but is for their convenience, and they only serve us because it suits their purpose to do so, as long as we serve them. Who shall draw the line between the parasites which are part of us, and the parasites which are not part of us? Or again, between the influence of those parasites which are within us, but are yet not _us_, and the external influence of other sentient beings and our fellow-men? There is no line possible. Everything melts away into everything else; there are no hard edges; it is only from a little distance that we see the effect as of individual features and existences.