MAN 305 



lack of exercise. This disease is due to nothing but a 

 lack of development and cannot be treated in any way. 

 (2) A defect may be acquired through accident. Man has 

 small power of regeneration when compared with many 

 other vertebrates. A salamander can replace a lost leg 

 but a man cannoc grow a single joint of a finger. Specializa- 

 tion has gone so far that the tissues remaining can at best 

 only close the wound. Accidents which maim or impair 

 the nervous system are most serious; a sudden shock or 

 strain may result in paralysis, insanity, or other perma- 

 nent disorders. (3) The machine may be without seri- 

 ous structural defects but fail to operate properly. The 

 digestive fluids may be too acid; excretions may not be 

 properly eliminated and poison the tissues; the mind may 

 not form sound deductions from observed phenomena. 

 (4) Many occupations are conducive to specific diseases 

 the Indian leads an active life with much exposure and has 

 his old age made unpleasant by rheumatism; the coal miner 

 has his lungs impaired by dust and bad air, hence often 

 acquires tuberculosis; the sedentary business man is dogged 

 by insomnia and indigestion. (5) Clothing may be a 

 source of diseases improper shoes often cause permanently 

 deformed feet; corsets may cause serious disturbances in 

 the digestive, circulatory, or reproductive organs. 



All the disorders mentioned up to this time are due to 

 some defect in man's structural mechanism or in its opera- 

 tion, but there is another class of diseases (6) which are 

 due to plant or animal parasites which actively invade the 

 body. The chief avenues for the entrance for such un- 

 desirable organisms are through the natural openings in 

 the skin, though some parasites enter in other ways (like 

 the tetanus bacillus which gains access through cuts, and 

 malaria which is injected hypodermically by mosquitoes). 

 Such diseases as cholera, typhoid, trichinosis, and tape- 

 worms, enter through the mouth with the food ; diphtheria, 

 infantile paralysis, tuberculosis, and some other diseases 

 are usually spread through nasal discharges; the eggs of 



