The treatment of the sick among the Laos ranks as a distinct profession. Although the Laos doctors may not have classified their knowledge of diseases in a way that we should call scientific, and although a white foreigner might be so unsolicitous of his own bodily welfare as to prefer the chance of nature to the professional skill of the whole Laos faculty, still, their system of medicine is quite an extensive one and embraces some very abstruse subjects. The Laos doctors are not required to have a diploma and do not attend any medical school, nor do they, as a rule, serve an apprenticeship; they just take to doctoring naturally. Some of them are widely known as successful general practitioners; others gain considerable notoriety in the treatment of certain diseases and become specialists of wide reputation. Some three or four medical books, treating of the mysteries of vital phenomena and learnedly elucidating the doctrine of the four elements, enrich Laos literature; these classic volumes also contain invaluable formulæ, and the doctor who is so fortunate as to own one of these books is held in high repute for his superior learning, notwithstanding he may not be able to decipher a line of it. Practically, the Laos, so far as the average doctor is concerned, have no medical treatises. The Laos are without a definite knowledge of any of the organs or functions of the human body; no Harvey or Sylvius has ever arisen among them. All of their theories concerning the bodily functions and the four elements are merely philosophic guesses. Imagination has taken the place of reason and experiment. Speculation furnishes them with a satisfactory solution of the problem, “Why is it that instead of flesh (muscles) only, tendons are found in the human body?” The Laos divide diseases into two classes. The first class includes all those disorders which may be considered as simply disturbances of equilibrium caused by an undue preponderance or diminution of one of the four elements――wind, fire, earth and water; the second class embraces all those more serious disorders of the human system which are due directly or indirectly to the influence of offended spirits.