RESPIRATION OF THE TISSUES 21 5 



the cells, instead of carbonic acid gas, and water, and urea 

 being formed, there are other products, some of which are 

 exceedingly poisonous and which the kidneys handle with 

 difficulty. The poisons retained in the circulation never 

 fail to produce their poisonous effects, as shown by head- 

 aches, clouded brain, pain, and weakness of the body. 

 The word intoxication means, "in a state of poisoning." 

 These poisons gradually accumulate as the alcohol takes 

 oxygen from the cells. The worst effects come last, when 

 the brain is too benumbed to judge fairly of their harm. 

 It is not true that alcohol in a small amount is beneficial. 

 A little is too much, if it takes oxygen which would 

 otherwise be available to oxidize wholesome food. 



369. Effects of tobacco. Tobacco smoke contains the 

 same kind of poisons as the tobacco, with other irritating 

 substances added. It is usually sucked into the mouth 

 and at once blown out again, but cigarette smoke is com- 

 monly drawn into the lungs and afterwards blown out 

 through the nose. It is irritating to the throat, causing 

 a cough and rendering it more liable to inflammation. If 

 inhaled into the bronchi, it produces still greater irritation, 

 and the vaporized nicotine is more readily absorbed as the 

 smoke is inhaled the more deeply. Cigarettes contain the 

 same poisons as other forms of tobacco, and often contain 

 other poisons which are added to flavor them. 



370. Respiration in birds. The lungs of all land ani- 

 mals are like man's lungs, and the process of respiration 

 is the same. The lungs of birds are fixed in the upper 

 part of the thorax, and in addition they are provided with 

 two smooth bags, each somewhat larger than the lung. 

 Each bag connects with the air sacs of the lung, and also 

 with the interior of the larger bones. Respiration can 

 occur in the bags and bones as well as in the lungs. 



