The far-away rivers of the world have all been traversed and mapped, but the streams of blood in the arteries of man are filled with the unknown. The habits of the Esquimaux, the customs of the dwarfs of Central Africa, the ways of the baboons of Sumatra are minutely set to book, but the wars of the phagocytes remain indeterminate, unexplained. With microscope to his eye the bacteriologist is now examining the constituent parts of the blood, isolating, breeding, and minutely studying the germs of fevers, the growths of tumors, and other elemental forms of human parasites, in order to discover their antagonisms, their likings; for in these jungles of the flesh the war of races proceeds quite as in the Amazonian forests--the white cells against the red, devouring, destroying. The men behind these bald, bleak doors are tireless workers as well as seers and sages. They toil (at ridiculously low salaries) in the avowed hope of eradicating diseases. They do not pause in dismay of the insoluble. They--or such as they--discovered the cure for small-pox, for hydrophobia, diphtheria, and for yellow-fever. They and their like brought chloroform to the woman in travail, and ether to the wounded soldier. They have enormously reduced the number of those who die on the battle-field by their antiseptic dressings, and by one discovery after another have made infantile diseases less destructive. They already control yellow-fever and are about to eradicate typhoid--yet they say "our work is but begun." Here one comes upon their dreams. Calm and contained as their words are, their hearts are aflame with passion for the undiscovered. They are akin to those who seek the theoretic poles of the earth, undaunted by endless defeats. With quickening breath they watch the electrons flame and fall, seeing the ultimate constitution of matter almost within their grasp, and yet they do not permit their dreams to blind or weaken them in their wearisome, hopeless quest. They have their heroism for humanity, too. They meet death face to face, as they pry close into the cause of decay, the secret of morbid growth. There is more danger in certain germs than in lions. Blood-poisoning is to the surgeon a more constant menace than hunger to an Arctic explorer. These students never know what destroyer they may unwittingly unloose. Cross-section of abnormal tissue is more entrancing than a rose-leaf, a cluster of bacilli more beautiful than a snowflake. They have gone past all creeds, these calm young men, but they bow before the unspeakable majesty of the unknown. To them the Hebrew Scriptures are but the tales of minstrels in the childhood of the race, Mohammed a dreamer of baseless visions, and Christ but incarnate love in an age of war. The Creator they conceive is too profound to admit of any attribute. He neither thinks nor feels, and the life that pulses at the base of the first faint cell is a part of the same power that binds the stars to their circling suns.