388 



CIRCULATION AND RESPIRATION 



te the organs of respiration. Their smoke contains not only the poison 

 of tobacco (nicotine), and poisonous gases like carbon monoxide 

 ("coal gas"), but also very irritating organic compounds called 

 aldehydes, which bring on the "hacking" cough of the cigarette user. 



Alcoholic liquors are likely to bring on weakness of the lungs, so that 

 the drinker is easily attacked by pneumonia and consumption. 



Tight clothing is a serious hindrance to good breathing. If clothing 

 is too tight about the chest, the chest cannot be enlarged properly in 

 inspiration. If it is too tight at the waist, it compresses the diaphragm, 

 the ribs, and the organs of the abdomen, and makes full breathing 

 impossible. 



392. The Skin. The skin (Fig. 291) serves as an out- 

 side covering for the body, protecting it from hurts, and 

 from the germs of disease that are constantly in the air. 



It consists of 2 layers: (1) 

 the true skin, or dermis; 

 (2) the outer skin, or cuticle. 

 The cuticle is also called the 

 epidermis, meaning, "upon 

 the dermis" (cf. 309). 



The epidermis consists of 

 transparent cells, and has no 

 nerves or blood vessels. It 

 forms a tough outside cover- 

 ing. The lower layer of epi- 

 dermis cells is in contact with 

 lymph (cf. 379), and from 

 it gets the nutriment that is 

 needed for the making of new 

 cells. These take the place of those rubbed off at the 

 surface (cf. 223). Where the skin is put to rough use, 

 as in the palms of the hands and the soles of the feet, the 



Epldermrs 



Fio. 291 

 Layers of the Skin, Greatly Magnified. 



