:86 TEE POPULAR SCIENCE' MONTELY. 



None of these functions must be overworked, as none of them must 

 fall short of their proper duty. Healthy, regular, daily action is their 

 law of life. If the brain and nervous system are overworked, vitality 

 is lowered, the resisting power of the body is diminished, disease is 

 easily produced. If *he brain and nervous system are underworked, 

 the generation of nervous power is low and deficient, the vitality of 

 the tissues becomes low in proportion, and disease is easily excited. 

 Overwork exhausts, ruins, kills the body, just as the continued gen- 

 eration of the galvanic current exhausts the acid and wears out the 

 zinc plate. The weakest point of the body has to bear the result of 

 this violation of Nature's laws. If the heart is that point, disease falls 

 upon it, and death before the legitimate term of man's existence is the 

 consequence. 



To keep the body in perfect health it must be duly oxygenated. 

 There must be free and ample interchange between the blood in the 

 lungs and the air entering the pulmonary cells. The life-stream must 

 be purified by its elimination of carbonic acid ; it must be vivified by 

 the absorption of oxygen. The fulfilment of these conditions demands 

 a full, free, and constant admission of pure air into the lungs. This full, 

 free, and constant admission of pure air cannot be obtained in badly- 

 ventilated houses, crowded buildings, schools as at present constructed, 

 theatres, manufactories, pits, underground railways, and the like. 



When the body has reached that age at which natural decay or 

 degeneration has begun, the absence of pure air hastens and increases 

 the degenerative tendency. Where the heart is more prone than other 

 organs to disease, the want of pure air falls with powerful effect upon 

 the tissues of the right heart. Their nutrition is defective by reason 

 of the impurity of the blood with which they are fed, their vital force 

 is lowered, their muscular fibre loses its tonicity, degeneration and de- 

 bility take the place of active nutrition and power. If in this condi- 

 tion any stress is thrown upon the heart by hurried walking, by lifting, 

 climbing, violent declamation, passional expression, singing, laughing, 

 or by any unusual exercise of the voice, the tricuspid valve gives way, 

 it henceforth fails to close its aperture, and the results of a back-flood- 

 ing of blood upon the venous system of the body begin to follow. If 

 none of these exciting causes occur, the continued breathing of impure 

 air is followed by constantly-progressing degeneration of the tissues 

 of the valves and muscular structure of the right heart ; they become 

 soft and feeble, their atoms shrink ; the segments of the> tricuspid are 

 at length unable to meet in their attempt to close their aperture; a 

 small chink or slit is left between them ; through this the blood finds 

 its way into the auricle above at every contraction of the heart ; and 

 soon regurgitation is followed by the secondary consequences produced 

 in the general system congestion of the liver, stomach, spleen, kid- 

 neys, bowels by haemorrhoids, general dropsy, and occasionally by 

 cerebral mischief. 



