October 26, 191 1] 



NATURE 



^7 



THE PHYSIOLOGY OF SUBMARINE WORK.' 



COMPRESSED air is used in all the great subaqueous 

 works of to-day, in tunnelling, harbour works, shaft- 

 sinking in wet soil, pier- and bridge-building, diving for 

 pearl and sponges, salvage work, &c. The intercommuni- 

 cation of the great cities of the world depends on tunnels 

 built with the aid of compressed air. All such works are 

 limited to a certain depth by the pathological effects pro- 

 duced on the workers. 



The Naked Diver. 



The naked diver preceded the diver who uses compressed 

 air. The body of the naked diver is pressed upon by the 

 water, equally and in all its parts, by a pressure equal to 

 one atmosphere (15 lb. per square inch) for every 33 feet 

 (10-3 m.) of depth. He takes a deep breath or two, fills 

 his lungs before, and holds his breath during, the dive. 

 He places a foot in a stirrup attached to a heavy stone, 

 and so is carried rapidly to the bottom. The air in his 

 lungs, air passages, and middle ear must be compressed 

 to half its volume at 33 feet (two atmospheres absolute), 

 to one-third at 66 feet (three atmospheres absolute), to a 

 quarter at 99 feet (four atmospheres absolute). The depths 

 attained are usually not greater than 60 to 70 feet. The 

 compression of the air in the lungs is rendered possible 

 by the upward movement of the diaphragm and sinking in 

 of the abdomen. Some of the air in the lungs must dis- 

 solve in the blood according to the law of partial pressures. 



The amount of nitrogen dissolved from air at one atmo- 

 sphere pressure and at body temperature is 085 per cent. 

 This is the figure for the watery part of the body. The 

 fat dissolves about 5 per cent., an important fact dis- 

 covered by Vernon. At 66 feet (three atmospheres) the 

 watery part can hold 085x3 and the fat 5x3 per cent. 

 Putting the fat against the solids of the body (bones, See), 

 which do not dissolve gas, it may be assumed that the 

 whole body dissolves about 1 per cent, of nitrogen per 

 atmosphere. A man weighing 60 kgm., then, will dissolve 

 when compressed from one to three atmospheres about 

 1300 c.c. of nitrogen, that is, if time were allowed for the 

 blood to convey the nitrogen from the lungs to the tissues 

 until saturation occurred. In the lungs there are about 

 4000 c.c. of air. Of course, far less than 1200 c.c. will be 

 dissolved in the minute the diver is submerged. In 

 addition to the solution of nitrogen, the blood will take up 

 more oxygen, both in solution and chemically combined 

 with the haemoglobin ; the diver working hard gathering 

 pearl or sponge will use oxygen rapidly. It is clear, then, 

 that the absolute volume of air must be reduced during 

 thr- minute the diver stays submerged, but it is difficult 

 to' estimate by how much. To allow for the reduction of 

 volume, both by compression and solution, in the body, it 

 is clear that the diver must fill his lungs well, otherwise 

 the diaphragm will be pushed up to such an extent that 

 the action of his heart and the circulation of the blood 

 become impeded. It is this, in part, which sets a limit 

 to the depth to which the naked diver can go. The bleed- 

 ings from mouth and nose which the unpractised naked 

 diver suffers are due, no doubt, to both the congestion of 

 the blood which results from holding the breath and to 

 rarefaction of the air in the nose and middle ear during 

 the ascent. Some time ago I put this question to Sir 

 E. Ray Lankester : What happens in the case of the whale 

 which sounds, perhaps, to a depth of 1000 feet? Does the 

 whale allow the lungs to fill with water as the air becomes 

 compressed to one-thirtieth of its volume? If not, what 

 is the mechanism engaged which permits such com- 

 pression? I fancy the whale allows water to enter, and 

 blows this out again when it ascends to the surface. The 

 naked diver can extend his stay under water by deep 

 breathing before the plunge and filling the lungs with 

 oxygen. The breathing is regulated by the concentration 

 of acid (or the hydrogen ion} in the blood — carbonic acid is 

 the natural end product of muscular metabolism : lactic 

 acid is produced in the muscles when there is a deficiency 

 of oxygen. Deep breathing before the dive will wasli out 

 much of the carbonic acid in the blood, owing to the in- 

 creased ventilation of the lungs. The blood and muscles, 



1 Evenms dijcour. 

 n Friday, Septembe 



: delivered before tbe Rritish A=<oi 

 1, by Mr. Leonard Hill, F.R.S. 



NO. 2191, VOL. 8/] 



too, will be better oxygenated, and thus less lactic acid will 

 be produced during the submergence. If oxygen is 

 breathed this will be still more the case, as Martin Flack 

 and I have shown. After deep breathing air for two 

 minutes we easily held our breath two or three minutes. 

 After deep breathing oxygen five minutes one of our sub- 

 jects held his breath more than eight minutes, and another 

 just above nine minutes. Taking a deep breath and then 

 holding it, J. M. pulled up a 60-lb. weight seventeen times 

 in twenty-three seconds before he was compelled to take 

 another breath. After deep breathing air for two minutes 

 he held his breath while he pulled it up thirty times in 

 fifty seconds, and after deep breathing oxygen for two 

 minutes, seventy times in eighty-five seconds. Similarly, 

 after a deep breath, R. A. R. held it while he ran 113 yards 

 in twenty-nine seconds ; 150 yards in 35! seconds after 

 deep breathing air for two minutes ; 25b yards in 62^ 

 seconds after deep breathing oxygen for two minutes. 

 S. E. ran on one breath 470 yards in no seconds after 

 deep breathing oxygen ! At the end he ran blindly, having 

 lost consciousness owing to the high concentration of COj 

 in his blood. 



The high pressure of oxygen in the lungs enables one 

 to hold one's breath until the pressure of CO, reaches 10 

 to n per cent., while if the pressure of oxygen is low a 

 breath must be taken when that of the CO, reaches no 

 more than half this amount. A balance is struck between 

 the relative pressures of oxygen and carbonic acid. Mr. 

 I. Feldman here has been breathing oxygen for some 

 minutes ; he will now put his face in a basin of water ; 

 you see he has now held his breath for three minutes 

 without the least trouble. 



It is clear, then, that the naked diver can stay longer 

 and do more efficient work if he deeply breathed and filled 

 his lungs with oxygen before each dive. 



I will demonstrate my little apparatus by means of 

 which oxygen can be generated from oxylithe (peroxide of 

 sodium) and inhaled. Two blocks of oxylithe are put in 

 the metal box — the generator — and a pint of water in the 

 rubber bag. The mouthpiece of the bag is clipped, and 

 the water allowed to enter the generator. Oxygen fills the 

 bag, and a solution of caustic soda is formed. The man 

 breathes in and out of the bag. This invention allows 

 oxygen to be carried about, and has proved useful for 

 mountain climbers who at high altitudes suffer from oxygen 

 want. 



Diving birds have double the normal volume of blood 

 (Bohr), just as the llama and the human inhabitant of 

 high altitudes have more red corpuscles and haemoglobin. 

 Observations on the blood of naked divers would probably 

 show the same increase. 



The Mechanical Effects of Pressure on the Body. 



The body of the naked diver at a depth of, say, 66 feet 

 is pressed upon equally on all sides by the Water, and by 

 a pressure of three atmospheres; for 33 feet of water = one 

 atmosphere. The gas in'his lungs (and intestines) is com- 

 pressed into one-third of its volume, and that is the only 

 effect of the pressure, for the pressure is transmitted equally 

 and instantly by the fluids of the body to all parts, and as 

 the fluids are practically incompressible the pressure has no 

 mechanical effect. 



The diver who uses gear, or the caisson worker, is 

 surrounded with compressed air, and breathes freely in it. 

 The body of either is pressed upon by the air, and the air 

 pressure' must always be just greater than that of the 

 water to keep the latter out of the dress, bell, or caisson. 

 I will demonstrate this on the model diver, diving bell, and 

 caisson. Whether it be air or water that uniformly presses 

 upon the body, the tissue fluids transmit the pressure equally ; 

 and thus, although it is computed that an extra atmosphere 

 means an additional total pressure of 15,000 to 20,000 kilo- 

 grams (40,000 lb.) On the body of a man. no mechanical 

 effect is produced. Living matter is a jelly containing 

 about 80 per cent, of water, and, like water, is practically 

 incompressible. Since attention was first directed to com- 

 pressed-air illness, the larger number of medical writers, 

 ignorant of physical laws, have supposed that exposure to 

 compressed air mechanically alters the distribution of the 

 blood, forcing it inwards and causing a congestion, which 

 is suddenlv and dangerously altered on decompression. 



