The heart may well be called the thermometer of the body. Under normal conditions it is never heard from, but under abnormal conditions it is the first and the most reliable sentinel of the body. It stands eternally on duty and sends its danger signals to the brain with truthful accuracy, whether the trouble be of physical, mental, or emotional origin. A word or a sound sent through the air enters the ear and is analyzed by the brain, but the heart registers accurately its effect upon the physical body. We see a face or an occurrence a block away, and through the optic nerves it is comprehended by the brain, but the heart alone registers or gives back to the brain the effect upon the body. [Sidenote: Necessity for heeding the symptoms of the heart] This little engine, but little bigger than one's fist, pumps about twenty tons of blood every day above its own level in every body of average size, besides sending the life fluids of the blood-serum with lightning speed to the parts of the remotest anatomy, carting away the effete and poisonous matter to the lungs to be burned with oxygen, and carrying new building material from cell to cell for repairs. Should we not, therefore, take good care of, and heed the warnings of so wonderful a piece of automatic mechanism? Should we not study all its symptoms told in a language sympathetic and truthful, and as unerring as the laws that govern the movement of worlds in space? [Sidenote: Some undefined technical terms] The heart gives off various symptoms indicating the different kinds of sins we commit against the natural laws of our organisms. Medical men have named some of these symptoms as follows: Dilation, hypertrophy, atrophy, aneurism, inflammation, valvular derangement, etc., but in none of their reference works are the causes of these so-called dis-eases clearly defined. Fatty degeneration is the only one that is explained, the term meaning that the heart has been deprived of room in which to do its work, owing to surrounding fatty accumulations. HEART TROUBLE--THE CAUSE The blood enters the heart through the superior venae cavae flowing to the right lobe or auricle, then it is pumped by the heart beats to the right ventricle. From here it is forced through the pulmonary artery to the lungs where it is purified and charged with the oxygen we breathe. From the lungs the blood returns through the pulmonary veins to the left auricle of the heart, and then to the left ventricle. Having passed once through the purifying plant and twice through the distributing station, it is now sent out through the large systematic artery and distributed to every capillary cell of the body. [Sidenote: Heart trouble caused by (carbon dioxid) gas]