424 Our Surroundings 



also produce internal secretions of great use to the body. The 

 pancreas is one of these glands. It has been found that this 

 organ not only discharges an important digestive fluid through 

 ducts into the intestine, but it also produces another substance 

 called insulin, which passes by diffusion directly into the blood. 

 Insulin, it seems, is necessary to other organs to insure assimila- 

 tion of sugar. Lack of production of this substance by the pan- 

 creas is the cause of the disease known as diabetes. 



Effect of Alcohol on Circulation. If taken in small 

 amounts alcohol sometimes increases the rate of the heart-beat. 

 The habitual use of alcohol is believed to cause the accumulation 

 of fat around the heart and within the heart muscle, producing 

 what is known as fatty degeneration of the heart. Large doses 

 may cause paralysis of the nerves of the heart, which may account 

 for heart failure. 



The continuous use of alcohol may cause dilation of the capil- 

 laries, increasing their blood capacity. The effect is often appar- 

 ent in the unusually red face of a person who drinks. This 

 dilation of blood vessels, seen in the capillaries of the face, goes 

 on throughout the arteries if the use of alcohol is coitinued. The 

 arteries are likely to lose their power of contraction and remain 

 dilated. Such a condition is said to favor secretion of lime in 

 the walls of the arteries, making them brittle, so that unusual 

 blood pressure may cause bursting of an artery, resulting in the 

 formation of a clot. If the clot is on the brain, as often happens, 

 the result is apoplexy, which is frequently fatal. 



Alcohol also has its effect on the blood itself. It injures the 

 white corpuscles and reduces their ability to fight disease germs. 



Effect of Tobacco Upon the Heart. Tobacco, when used 

 extensively, acts as a poison on the nerves of the heart, causing it 

 to beat irregularly and rendering close application to work arduous 

 on account of palpitation. The habitual use of cigarettes by boys 

 has a harmful effect on the quality of the blood, causing inade- 

 quate respiration of the cells, thus hindering the release of energy 

 necessary for the best physical and mental development. 



Assimilation. Assimilation is the process of changing the 

 digested food into Jiving tissue. It takes place in the cells through- 



