HEART 



2747 



HEAT 



provinces the laws require that pupils in 

 their physiology classes be taught the . harm- 

 ful ' effects of strong drink. 



The use of to- 

 bacco is also to 

 be condemned. 

 A surgeon-general 

 of the United 

 States army has 

 reported that 

 candidates for 

 West Point who 

 are annually re- 

 jected because of 

 irregularities of 

 the heart's action 

 are nearly a 1 1 

 users of tobacco. 



Plenty of whole- COURgE Qp THE BLOQD 

 some, nutritious, (1>2 ) Superior and inferior 

 digestible food (3) Rlgh -- e rIC C , a e Vae 

 and abstinence (4) Right ventricle 

 e i i i i (5, 5, 5) Pulmonary veins 



from alcohol and (6 6) p u i m0 nary veins 

 tobacco will <?> Left auricle 



(8) Left ventricle 

 help to keep the o) Aorta 

 heart strr.no- nnH (10 > Innominate artery 

 heart strong and (11) Left carotid artery 



active. (!2) Left subclavian artery 



Diseases of the Heart. The term heart dis- 

 ease includes several maladies of the organ 

 itself, and also various irregularities in its 

 action due to disease in other parts of the body 

 and to wrong habits of living. Palpitation of 

 the heart, in which the pulse beats may num- 

 ber 150 or more a minute, may be produced by 

 certain nervous disorders, by overindulgence 

 in stimulants or by excessive physical or emo- 

 tional strain. Heart spasm is an acutely pain- 

 ful malady supposed to be caused by disease 

 of the coronary arteries. Poisons in the blood, 

 which affect the muscles, lining or valves of 

 the heart, are responsible for a number of 

 diseases peculiar to that organ. Important 

 among these are myocarditis, inflammation of 

 the muscular layer of the heart walls; and 

 endocarditis, inflammation of the lining mem- 

 brane. The latter very often is a complication 

 of rheumatism, but is also caused by scarlet 

 fever, pneumonia and other infectious diseases. 

 As in endocarditis the inflammation is usually 

 confined to the membrane which covers the 

 valves of the heart, this malady is often known 

 as valvular heart disease. Sometimes the 

 valves become stiff and obstruct the flow of 

 blood, and sometimes the flaps become so 

 shortened by contracting that they allow the 

 blood to flow backwards even when the valves 



are closed. The latter condition is called re- 

 gurgitation, which means passing backwards. 



Pericarditis is inflammation of the bag en- 

 closing the heart, causing that membrane to 

 become thickened and roughened, and often 

 seriously impeding the heart's action. Enlarge- 

 ment of the walls of the heart (hypertrophy), 

 in which the weight of the organ sometimes 

 increases to two or three pounds, may be 

 caused by mountain climbing or by emotional 

 strain. This condition also frequently follows 

 kidney trouble. It is not as a rule dangerous, 

 but becomes so if fatty degeneration also takes 

 place. Compared with other diseases, those of 

 the heart are not a frequent cause of death. 

 Even a person who has chronic valvular trouble 

 may expect to live his allotted number of 

 years if he avoids violent exercise, controls his 

 emotions, eats wholesome, nutritious food and 

 avoids stimulants and narcotics. S.C.B. 



Related 'Subjects. A better understanding of 

 the heart and its work may be gained from the 

 following articles : 



Angina Pectoris Circulation of the Blood 



Aorta Membranes 



Arteries Pericardium 



Blood Pulse 



Capillaries Veins 



HEAT. Everyone is familiar with the sen- 

 sations produced by what are termed heat and 

 cold. The study of these so-called "heat- 

 effects" and of the laws according to which 

 they are produced forms what is known in 

 physics as heat. 



What Heat Is. Every substance, whether 

 solid, liquid or in the form of gas, consists of 

 a great number of small particles called mole- 

 cules. These molecules are constantly in mo- 

 tion, and heat is the energy produced by the 

 agitation of these molecules. When their mo- 

 tion is very rapid, a substance is said to be 

 hot; when it is less rapid, the substance is 

 said to be cool or cold. The point at which 

 all molecular motion would cease is called 

 absolute zero, but this is purely theoretical 

 it is a degree of coldness that has never been 

 reached. 



Where Heat Comes From. (1) Most of the 

 energy or heat that is available for use comes 

 either directly or indirectly from the sun. All 

 plant life and all animal life depend for their 

 existence on this great, white-hot ball around 

 which our world revolves. If the sun, which 

 is estimated to have a temperature of about 

 10,000 F., should cool, all life would be ex- 

 tinguished and the earth would become a cold, 

 dead mass like the moon. 



