_Note._ Let the pupil review the anatomy and physiology of the circulatory organs from fig. 75, or from anatomical outline plates, No. 6 and 7. CHAPTER XIX. HYGIENE OF THE CIRCULATORY ORGANS 367. If any part of the system is deprived of blood, its vitality will cease; but, if the blood is lessened in quantity to a limited extent, only the vigor and health of the part will be impaired. The following conditions, if observed, will favor the free and regular supply of blood to all portions of the system. 368. _The clothing should be loosely worn._ Compression of any kind impedes the passage of blood through the vessels of the compressed portion. Hence, no article of apparel should be worn so as to prevent a free flow of blood through every organ of the body. 369. The blood which passes to and from the brain, flows through the vessels of the neck. If the dressing of this part of the body is close, the circulation will be impeded, and the functions of the brain will be impaired. This remark is particularly important to scholars, public speakers, and individuals predisposed to apoplexy, and other diseases of the brain. 370. As many of the large veins lie immediately beneath the skin, through which the blood is returned from the lower extremities, if the ligatures used to retain the hose, or any other article of apparel, in proper position, be tight and inelastic, the passage of blood through these vessels will be obstructed, producing, by their distention, the varicose, or enlarged veins. Hence elastic bands should always be used for these purposes. -=-=-=-=-=-=-=-=-=-=-=-= 367-386. _Give the hygiene of the circulatory organs._ 367. What effect will be produced on the body if it is deprived of blood? If the blood is only lessened in quantity? 368. Why should the clothing be worn loose? 369. What is said of dressing the neck? To what persons is this remark applicable? 370. How are enlarged veins frequently produced? -=-=-=-=-=-=-=-=-=-=-=-= 371. _An equal temperature of all parts of the system promotes health._ A chill on one portion of the body diminishes the size of its circulating vessels, and the blood which should distend and stimulate the chilled part, will accumulate in other organs. The deficiency of blood in the chilled portion induces weakness, while the superabundance of sanguineous fluid may cause disease in another part of the system. 372. _The skin should be kept not only of an equal, but at its natural temperature._ If the skin is not kept warm by adequate clothing, so that chills shall not produce a contraction of the blood-vessels and a consequent paleness, the blood will recede from the surface of the body, and accumulate in the internal organs. Cleanliness of the skin is likewise necessary, for the reason, that this condition favors the free action of the cutaneous vessels.