October 26, 191 ij 



NATURE 



573 



nervous system compressing the nerve cells. As the bubbles 

 are oxygen, the cells do not die, and the animals may re- 

 cover, the oxygen being absorbed by the tissues and the circu- 

 lation re-established. (4) +3 atmospheres oxygen convulsed 

 animals in thirty to sixty minutes (Bert and Lorrain 

 Smith), and the poisonous effect, depending as it does on 

 the partial pressure ol oxygen in the blood, comes on just 

 as soon in larger animals as in small, e.g. cats, rats, and 

 mice. (5J Fatal inflammation of the lung is produced by 

 exposure to high partial pressures of oxygen, e.g. after 

 twenty-five hours' continuous exposure to +7 atmospheres 

 of air=i70 per cent, atmospheric oxygen (Lorrain Smith). 

 This can be prevented by using nitrogen to dilute the air, 

 and so lowering the partial pressure of oxygen, (b) It is 

 quit.' safe to breathe one atmosphere oxygen, or five atmo- 

 spheres air, for three to four hours. The men who wear 

 the Fleuss apparatus for rescue work in mines have breathed 

 it day after day for this period. 1 have spent much time 

 with Mr. R. ri. Davis in perfecting this apparatus on 

 physiological lines, and so have studied particularly the 

 effect ot oxygen on man. In very hard work there may 

 be a deficiency of the oxygen supply in the body, and 

 then breathing oxygen helps the working power of the 

 man. 



If the body is getting enough oxygen the breathing of 

 it has no effect on the metabolism. The man at rest 

 cannot be fanned into a greater rate of activity by breath- 

 ing oxygen. Poisonous pressures of oxygen lower the 

 metabolism and diminish the carbonic acid output of 

 animals. Martin Flack and 1 showed that the breathing 

 of oxygen just before a race may help an athlete, because 

 during his great effort he uses up oxygen quicker than his 

 respiration and circulation can provide it. A shortage of 

 oxygen leads to the production of acid products in the 

 tissues and blood, which causes breathlessness and stiff- 

 ness "I the muscles. 



Lactic acid appears in the urine after a short period of 

 hard running (Ruffel). Feldman and I have found that 

 breathing oxygen by means of the Fleuss dress during 

 1 lie run prevents the excretion or lessens the amount of 

 lactic acid excreted. Thus the pressure of oxygen helps 

 the caisson worker to do his work more easily. During 

 decompression the pressure of oxygen is lowered, and this 

 is of no advantage to him. 



Bornstein at the Elbe Tunnel works has breathed 

 oxygen (90 to 95 per cent.) for forty-eight minutes at a 

 pressure of three atmospheres. Two other engineers 

 breathed it for thirty minutes. Bornstein freed himself 

 from " bends " by this means. These periods are the out- 

 side limits of safety. Bornstein began to have slight con- 

 vulsive movements. 



For everv atmosphere the body dissolves nitrogen to 

 about 1 per cent, of its mass — for a 60 kgm. man, say, 

 600 to 1000 c.c. per atmosphere. Von Schrotter calculates 

 that oxygen plus exercise would turn out 1000 c.c. in five 

 minutes, probably more. 



Oxygen can be breathed economically bv means of the 

 Fleuss apparatus, which was used so effectively in the last 

 great colliery disaster at Bolton. The apparatus can be 

 put on and oxygen breathed for ten minutes before and 

 during decompression. The breathing-bag must be 

 washed out several times with a current of oxygen, from 

 the emergency valve provided, to accelerate the output of 

 nitrogen. 



J. F. Twort and I have investigated the effect of breath- 

 ing oxygen on the volume of nitrogen dissolved in the 

 urine. Precautions were taken to collect the urine with- 

 out contact with the atmosphere. About three pints of 

 water were drunk thirty minutes before collection of 

 urine, so that samples could be obtained every seven 

 minutes or so. The sample- were pumped out bv means 

 of the Gardner and Buckmaster gas-pump, in which thpre 

 are no taps, and leakage of air is practicallv nil. 



I cite the results of two experiments. 



(1) Breathed air at three atmospheres. After fifteen 

 minutes emptied bladder. Sample I. collected seven 

 minutes later at three atmospheres. Decompressed to 

 ij atmospheres in threp minutes. Sample II. collected six 

 minutes later at ij atmospheres. Decompressed to one 

 atmosphere in thre" minutes. Sample III. collected three 

 minutes Inter at one atmosphere. 

 NO. 2IQI, VOL. 87I 



(2) At three atmospheres lor forty-four minutes. 



Emptied bladder and breathed oxygen for nine minutes, 



then took Sample I. Decompressed to i| atmospheres in 



two minutes. Took Sample II. four minutes later. 



Decompressed to one atmosphere in iA minutes. Took 



Sample III. five minutes later. 



., . ~ Pressure Nitrogen 



Nurogen Oxygen aim ca l cu |t, =d 



Sample I. ... 2-091 0297 3 255 



,, II. ... 0-8835 0-1985 I?: 1-416 

 ,, 111. ... 0-5751 00941 1 0-85 



The results show that the urine is supersaturated with 

 nitrogen after decompression in the first case, and under- 

 saturated after breathing oxygen in the second case. 



The ideal method, then, for safe decompression from 

 high pressure is (1) oxygen breathing for five minutes and 

 rapid decompression to two atmospheres ; (2) pause during 

 which oxygen is breathed and exercise taken ; (3) rapid 

 decompression to one atmosphere while oxygen breathing 

 and exercise are continued. 



The period of decompression can be notably shortened 

 by such means, how far further experiment will show. 

 VVe want to know, in particular, how the fat of the 

 spina! cord is desaturated under these conditions. The 

 " quick " parts are evidently put right in a few minutes. 

 Further experiments on fat pigs should give the required 

 information. 



Recompression. 



Recompression is the one method of cure for the ill- 

 ness. Pol and Watelle (1854) recorded the benefit of this. 

 Men with " bends " went back under pressure. A. Smith 

 suggested the use of a recompression chamber at Brooklyn. 

 E. W. Moir instituted it at the Hudson Tunnel. All 

 caisson works are now provided with such. Men at the 

 East River Tunnel works have truly been raised from the 

 dead by its means. 



In the frog's web experiment I have observed the bubbles 

 shrink up on recompression. Experiments on animals 

 show that recompression must be applied at once in 

 dangerous cases, before vital parts are killed by the inter- 

 ference with the circulation. " Bends " may be relieved 

 by compression long after they have come on. 



Recompression relieved 90 per cent, of the cases at the 

 East River Tunnel, and all but 0-5 per cent, were partly 

 relieved by its means. Oxygen breathing can be employed 

 with advantage in the medical lock. Decompression from 

 the lock must be slow, for some of the bubbles, having 

 run together to form larger ones, only shrink up on re- 

 compression, and do not quickly go into solution. These 

 expand again on decompression. J. F. Twort and I have 

 observed this happening, and measured the bubbles under 

 the microscope. 



For deep-diving work a recompression chamber should 

 always be at hand. I have contrived a double-chambered 

 diving bell, one chamber open to the sea, the other closed, 

 save for a manhole communicating with the first. The 

 divers after completing their work enter the inner chamber 

 and close the manhole. The bell is raised on deck, and 

 the men decompressed by the stage method. Such a con- 

 trivance prevents exposure to cold during, or risk of storm 

 preventing, gradual decompression in the ordinary way by 

 the diver climbing the shotted rope. 



UNIVERSITY AND EOVCATIONAL 

 INTELLIGENCE. 



Bristol.— The annual Congregation for the presentation 

 of degrees was held on Friday, October 20. After the 

 deans had presented the graduands in the various faculties, 

 the following honorary degrees were conferred : — Doctor 

 of Letters: Prof. Alfred Marshall; Doctor of Science: Mr. 

 Arthur Prince Chattock, Prof. Julius Wertheimer, and Sir 

 William Ramsav. The recipients of the science degree 



