106 



RESPIRATION 



exterior into the cavity of the water-vascular system. Another 

 exam23le of the same sort of trouble is that of the honey bee, 

 which is infested at times with a certain small mite living in 

 its tracheae. Its presence is a serious interference with the 

 proper breathing of the bee, which is 

 often killed by choking. 



The amount of soot and dust in 

 the air, owing to the fact that what 

 laws we have are not enforced and 

 are in themselves inadequate, is 

 shown by the fact that, in the month 

 of June alone, no fewer than 54 tons of 

 dirt of various kinds were deposited from 

 the air in the City of London, which covers 

 an area of one square mile. Of this mass 

 of dirt, approximately eighteen tons were 

 soluble, and included sulphates, chlorine, 

 and ammonia, and thirty-six tons were 

 insoluble, and consisted of tar, soot, and 

 grit. 



There could scarcely be a more severe 

 indictment of our present methods. For 

 the inhalation of grit and tar is certainly 

 dangerous, while the "smoke screen" 

 shuts out the sun-light from our streets. 

 There can be no doubt that great injury 

 is inflicted on animals and plants by this 

 impurity and pollution, and that until it 



has been removed we shall fall far short tedon ^acoda." A young 

 of even a moderate standard of public individual magnified 1^. 

 health. Pure, sunny air, indeed, is the ^*^^ Carpenter. 

 greatest need of city-dwellers at the present moment. The 

 withholding of it, on any pretext, is unjustifiable. 



Dove va 11 Sole non va il Medico. 



Fig. 34. A Sea-lily, An- 



Haemoglobin 



We have seen that in insects, spiders, centipedes, etc., 

 oxygen is conveyed direct to the living cells without any 



