The functions of the several organs concerned in digestion have their activity increased by sleep. The blood which leaves the brain, goes, as Durham has shown, to the stomach and other abdominal viscera, and hence the quantities of the digestive juices are augmented, and the absorption of the nutritious elements of the food is promoted. The urine is excreted in less quantity during sleep than when the individual is awake and engaged in mental or physical employment, because the wear and tear of the system is at its minimum. The perspiration is likewise reduced in amount by sleep. In warm weather, however, the effort to go to sleep often causes an increase in the quantity of this excretion, just as would any other mental or bodily exertion. This circumstance has led some writers to a conclusion the reverse of that just expressed. Others, again, have accepted the doctrine of Sanctorius on this point without stopping to inquire into its correctness. This author,[31] among other aphorisms relating to sleep, gives the following: “Undisturbed sleep is so great a promoter of perspiration, that in the space of seven hours, fifty ounces of the concocted perspirable matter do commonly exhale out of strong bodies. “A man sleeping the space of seven hours is wont, insensibly, healthfully, and without any violence, to perspire twice as much as one awake.” The observations of Sanctorius with his weighing chair led to a good many important results, but they were inexact so far as the function of the skin was concerned, in that they made no division between the loss by this channel and that which takes place through the lungs, for by perspiration in the above quotations he means not only the exhalation from the skin, but the products of respiration--aqueous vapor, carbonic acid, etc. His apparatus was, besides, very imperfect, and could not possibly have given the delicate indications which the subject requires. Whether the condition of sleep promotes the absorption of morbid growths and accumulations of fluids is very doubtful. Macnish[32] contends that it does, but _a priori_ reasoning would rather lead us to an opposite conclusion. Deficiencies are probably more rapidly made up during sleep than during wakefulness, and thus ulcers heal with more rapidity, owing to the increased formation of granulations which takes place; but the removal of tumors, etc. by natural process involves the operation of forces the very opposite of those concerned in reparation, and observation teaches us that sleep is a condition peculiarly favorable to the deposition of the materials constituting morbid growths. Some writers have alleged that sleep accelerates the absorption of dropsical effusions, but the disappearance of such accumulations during the condition in question is clearly due to the mechanical causes depending upon the position of the body.