1907.] Fats, and its Relation to Caisson Disease. 369 



olive oil one of about 83 per cent., it follows that the proportion of unsaturated 

 acids present in a fat has little or no influence upon its solvent powers for 

 oxygen and nitrogen. 



From the absorption coefficients for oxygen and nitrogen given by Bohr 

 and Bock* it is calculated that 100 c.c. of water saturated with air at 

 15° absorb 0*733 c.c. of oxygen and 1*411 c.c. of nitrogen. Taking a mean 

 of all the values obtained with cod liver oil and olive oil at 15°, the solubility 

 of oxygen is found to be 3*1 times greater than in water, and of nitrogen 

 3*7 times greater. At 37° Bohr and Bock's values show that 100 c.c. of 

 water absorb 0*507 c.c. of oxygen, and 0*975 c.c. of nitrogen. Taking 

 a mean of all the values obtained with cod liver oil and olive oil at 37°, and 

 with lard at 45° (for doubtless the solubility at this temperature is practically 

 the same as at 37°), the solubility of oxygen is found to be 45 times greater 

 than in water, and that of nitrogen 5*3 times greater. It has been found 

 by Bohr,*f that blood plasma dissolves 2*5 per cent, less nitrogen than an 

 equal volume of water, whilst blood dissolves slightly less still ; hence we 

 may conclude that at body temperature the fat of mammals dissolves at least 

 five limes as much nitrogen as water or as blood and blood plasma. 



The solubility of oxygen in fats, though apparently less than that of 

 nitrogen, may in reality be as great. It is well known that oils are able to 

 absorb and combine with oxygen, and the rate of this absorption is by no 

 means inconsiderable. For instance, a sample of olive oil was saturated with 

 air at 15°, and was kept for 23 hours at 18° in a stoppered bottle filled to 

 the brim. It then yielded only 0*49 c.c. of oxygen per 100 c.c, whilst some 

 of the sample from which the air was boiled off an hour after saturation 

 yielded 2*40 c.c. Owing to its richness in unsaturated acids, cod liver oil 

 absorbs oxygen more quickly still, and a sample saturated with air at 15°, 

 and kept 23 hours at 18° in a stoppered bottle, gave only 0*05 c.c. of oxygen 

 per 100 c.c. Undoubtedly, therefore, there must have been some absorption of 

 dissolved oxygen during the half to one and a-half hours the air-saturated 

 oils were kept before analysis. 



It might be thought that the solubilities determined by the above described 

 method are invalidated, or liable to be invalidated, by leakage of air into the 

 vacuum pump. This is not the case if due precautions are taken. The 

 pump must be in such good order that no appreciable leakage occurs when it 

 is left vacuous for several days, and it must be kept vacuous for a week or 

 more before use, for if air be left in it a small amount attaches itself to the 

 glass walls of the apparatus, and only escapes slowly when the pump is 



* Bohr and Bock, ' Wied. Ann./ vol. 14, p. 318, 1891. 

 t Bohr, < Nagel's Handb. d. Physiol.,' vol. 1, p. 62, 1905. 



