The personnel is nearly as complicated as the material. Not only are there all the various ranks of commissioned officers in the line, medical corps, pay corps, marine corps, etc., but there are ten kinds of warrant officers besides; while in the enlisted personnel there are ninety-one different "ratings" in the navy, and thirteen in the marine corps, besides temporary ratings, such as gun-pointer, gun-trainer, gun-captain, etc. Each rank and rating carries its rigidly prescribed duties, as well as its distinctive uniform and pay. That such a multitudinous host of types and individuals, both material and personnel, can be actually combined in one unit fleet, and that fleet operated as a mobile directable organism by its admiral, is a high achievement of the human intellect. How is it done? By discipline, by training, by knowledge, by energy, by devotion, by will; by the exercise of those mental, moral, and spiritual faculties that may be grouped under the one term "mind": the same power that co-ordinates and controls a still more complex machine, the organism of the human body. Despite its relative crudeness, a fleet possesses, more fully than any other fruit of man's endeavor, the characteristics of an organism, defined by Webster as "an individual constituted to carry on the activities of life by means of parts or organs more or less separate in function, but mutually dependent." And though it must be true that no fleet can approximate the perfection of nature's organisms, nevertheless there is an analogy which may help us to see how a complex fleet of complex vessels has been slowly evolved from the simple galley fleets of earlier days; how its various parts may be mutually dependent yet severally independent; and how all must be made to work as one vast unit, and directed as one vast unit by the controlling mind toward "the end in view." The common idea is that an army consists of a number of soldiers, and a navy of a number of ships. This idea is due to a failure to realize that soldiers and ships are merely instruments, and that they are useless instruments unless directed by a trained intelligence: that the first essential in an army and the first essential in a navy is mind, which first correctly estimates the situation, then makes wise plans to meet it, then carries out those plans; which organizes the men and designs the ships, and then directs the physical power exertable by the men and the ships toward "the end in view."