370 Dr. H. M. Vernon. Solubility of Air in [Apr. 1, 



made vacuous again. Air likewise attaches itself to the walls of the boiling 

 flask, but it is got rid of by the preliminary boiling of the dilute acid previous 

 to the introduction of the oil. In all analyses of gases, whether in oil, water, 

 or salt solutions, such a preliminary boiling was invariably adopted, and by 

 taking these precautions many hundreds of analyses have been made without 

 invalidation of results by leakage of air. I have elsewhere* recorded nearly 

 a hundred analyses of the gases in sea water, and the mean nitrogen values 

 then obtained are almost identical with the nitrogen absorption values 

 determined by Dittmar. 



The bearing of the above recorded results upon many phases of caisson 

 disease is probably a direct one. The commonest symptoms observed in 

 caissoniers consist of joint and muscular pains, and in paralysis, the latter 

 being the result of injury to the spinal cord. Thus in autopsies of caissoniers, 

 Bert observed softening of some inches of the spinal cord in the dorsal region. 

 v. Leyden, in a case of death 15 days after decompression, observed signs of 

 myelitis, and small irregular fissures in the mid-dorsal cord, probably 

 produced by the escape of gas. Autopsies of divers have shown necrobiosis 

 and haemorrhages in the spinal cord,f and distention of the blood vessels by 

 air bubbles.^ 



Chemical analysis shows that spinal cord and peripheral nerves contain 

 nearly 20 per cent, of fat and fat-like substances. Adipose tissue contains 

 about 83 per cent, of fat, and yellow bone marrow (as distinct from red 

 marrow, which is poor in fat) contains no less than 96 per cent, of fat 

 (Gorup-Besanez). If these tissues were saturated with nitrogen at, for 

 instance, four atmospheres of atmospheric pressure, 100 c.c. of them would 

 contain, instead of the 0*975 x 4 = 3'90 c.c. of dissolved nitrogen present in 

 an equal volume of water, about 7 c.c. in the case of the spinal cord and 

 nerve, and 20 c.c. in the case of yellow bone marrow. On sudden 

 decompression, therefore, the volume of nitrogen bubbling off in a gaseous 

 form might be two to six times as much as that from the non-fatty fluids and 

 tissues of the body. 



It has been found that the severity of the symptoms developed by 

 caissoniers is influenced greatly by the time of exposure to increased pressure. 

 In sinking the foundations of a bridge at St. Louis, a pressure reaching at 

 a maximum to 50 lbs. above normal was used, and a large proportion of the 

 workers were affected. As the depth of the caissons increased, the shifts 

 were shortened from four hours to one hour, with the result that the serious 



* Vernon, ' Journ. Physiol./ vol. 19, p. 68, 1895. 



t Cited by Hill and Macleod, ' Journ. Hygiene,' vol. 3, pp. 408 and 409, 1903. 



\ See Hill's " Eecent Advances in Physiology," p. 250, 1906. 



