326 DISTURBAyCES OF CIRCULATION 



intercellular openings. Fat may also escape in the bile, and some is 

 probably taken up by the tissue and endothelial cells by phagocytosis. 

 Beneke found that the fat becomes partly emulsified by the mechanical 

 action of the blood current, aided to a slight extent by saponification. 

 The larger droplets after lodging in the capillaries are surrounded 

 by leucocytes, to which Beneke ascribes an active part in the removal 

 of the fat as fine droplets by phagocytic action. We may well believe, 

 however, that the lipase of the plasma is an important agent in disin- 

 tegrating the emboli, although its action is limited because of the rel- 

 atively small surface which the large drops offer for attack. After 

 fat droplets have been taken into the cells, they presumably are util- 

 ized in metabolism like normally acquired fat. as described previously. 



The amount of fat free in the blood in fat embolism may be sur- 

 prisingly large. Bissell ^'^^ found from 2 to 6.5 per cent, in the venous 

 blood of several typical cases, although sometimes figures within normal 

 limits (0.2 to 0.6 per cent.) were found. The higher quantities repre- 

 sent such a great amount of free fat in the blood, even witliout con- 

 sidering the quantity held in the capillaries, that it is scarcely possible 

 for it all to have come from the fractured bones. 



Air embolism presents some features of interest from the chemical 

 standpoint, especially in those cases following sudden decrease in at- 

 mospheric pressure in persons who have been exposed for some time to 

 pressures considerably higher than that of the atmosphere (diver's 

 palsy, caisson disease, etc.). This form of air embolism is due to the 

 fact that fluids can dissolve much more gas at high pressures than at 

 low pressures; consequently when the abnormally great pressure to 

 which divers, caisson workers, etc., are subjected is too suddenly re- 

 duced to that of the atmosphere, the excessive gas that was absorbed 

 during the period of high pressure by the blood and tissue fluids is 

 released, and forms bubbles in the tissues and blood. The bubbles in 

 the nervous tissues may cause paralyses of various sorts, or death; 

 those in the blood may, if in sufficient amount, cause serious or fatal 

 capillary obstruction. The bubbles consist chiefly of nitrogen, be- 

 cause the power of the blood to hold oxygen in combination is so great 

 that not much of this gas becomes freed.'^* The body fluids of normal 

 persons contain about 675 c.c. of nitrogen, all told, but at 22 pounds 

 pressure this is increased to 1350 c.c, while but about 50 c.c. of free 

 oxygen would be present (Langlois). Carbon dioxide is so readily 

 combined in the blood that none is free even at high pressure, al- 

 though ]\IcWhorter "" reports that the gas collected from the right side 

 of the heart in a fatal case contained 20 per cent. CO, and 80 per cent, 

 nitrogen. Possibly some oxygen may also be released from solution 



iTb.Tour. Amer. Med. Assoc, IIUC) (Cu), l!>-2<>. 



ns Tliis subject is fully discussed by Leonard Hill in ■rvccciit Advances in 

 Physiolof^v and Biocliemistrv," T»ndon, 190G. 



eoAmer. Jour. Med. Sci., 'lOlO (130), 373; Erdman. ibid., V^\^^ (145). friO. 



