THE WORLD'S ADVANCE 



A Diver Taking a Sample of Air from His Helmet 



in Order to Determine the Amount of Carbonic 



Acid Present at Varying Depths. 



Why has it taken so long to make this 

 possible? Or, rather, how has the 

 human body thus suddenly acquired new 

 powers of endurance? Let us go back 

 to the investigations conducted by the 

 British Admiralty's Committee. 



The researches were inspired by a 

 number of deaths among the seamen 

 divers in the Royal Navy, and what made 

 the losses more distressing was that the 

 men seemed to be alright for a period 

 after returning to the surface and then 

 keeled over and died without any ap- 

 parent reason. There was a reason, but 

 its identity had not been clearly deter- 

 mined previously ; so the scientists of that 

 committee set out to unravel nature's 

 puzzle. And we shall see how vital a 

 part animals played in the preliminary 

 experiments leading up to certain amaz- 

 ing tests in which some of the investi- 

 gators subjected themselves to abnormal 

 and hitherto unreached pressures. 



First the physicians studied the ef- 

 fects of increasing air pressure upon 

 small animals, such as rats and mice and 

 rabbits and guinea pigs, and, at the same 

 time, watched their antics or what hap- 

 pened to them when the pressures were 



suddenly reduced to the atmospheric 

 normal. From these investigations some- 

 thing was learned, but the data was in- 

 conclusive and the causes not definitely 

 established. Accordingly, it was then 

 decided to use larger warm-blooded crea- 

 tures which would enable the research- 

 ers to arrive at more pronounced quan- 

 titative results, and for this work they 

 chose goats. These larger mammals fur- 

 nished the exact information needed, and 

 then the physicians themselves did not 

 hesitate to go into a testing cylinder and 

 submit to air pressures corresponding to 

 those called for in a diving suit when 

 submerged at depths of from 150 to 210 

 feet in the sea. 



The air we breathe contains nearly 80 

 per cent, of nitrogen, and this is the ele- 

 ment in the atmosphere that endangers 

 the pressure worker primarily, and it ex- 

 erts its hurtful tendencies after the diver 

 or the "sand-hog" has returned to the 

 normal air. Bubbles of nitrogen develop 

 in the tissues, in the smallest of the blood 

 vessels, in the fluids of the joints, and in 

 the nerve substances. These bubbles 

 either interrupt circulation or cause pres- 

 sures the first leading to asphyxiation 

 and stoppage of the heart, while the latter 

 produces paralysis or the lesser evil com- 

 monly termed "the bends." Now these 

 bubbles do not evolve within the body 

 while it is undergoing pressure, nor do 

 they usually manifest themselves during 

 the stages of decompression, but they be- 

 tray their presence by various symptoms 

 when the pressure upon the diver or the 

 caisson worker has been relieved. The 

 effects may not be felt until many hours 

 later. 



The blood in our bodies does not make 

 a complete cycle to every part of our 

 physique in the same period. It pene- 

 trates much slower into the tissues and 

 parts fed and drained by the tiny capil- 

 laries, and, in turn, it flows from these 

 remote sections of our anatomy with cor- 

 responding sluggishness. The active ar- 

 teries and veins, on the other hand, ab- 

 sorb faster and give off more rapidly 

 the elements of the air breathed, and, 

 therefore, respond more speedily to the 

 rise or fall of external pressure. Now 

 what happens? The capillaries and the 

 tissues fed by them lag in reaccommodat- 



