856 SPECIAL PHYSIOLOGY. 



acid given off from, the venous blood reaching those organs; these re- 

 newed chemical changes in the blood, induce again its onward motion 

 through the capillaries into the pulmonary veins ; thence it flows on, 

 more or less oxygenated, into the left side of the heart, which resumes 

 contractions of sufficient strength to propel this oxygenated blood into 

 the nutrient arteries of the heart and its ganglia, as well as into the 

 muscular and nervous systems generally. In this way, the rhythmic 

 power of the heart itself, and the excitability of the respiratory nerves, 

 the nervous centres, and muscles, are restored, and, subsequently, 

 conscious sensation, perception, and volition. In the meantime, more- 

 over, the respiration of the capillary circulation in the lungs, liberates 

 the blood previously pent up in the right cavities of the heart, gradu- 

 ally unloads those cavities, facilitates more and more, at each moment, 

 their free action, and so, by degrees, empties the over-distended ve- 

 nous system. The freer return of the blood from the systemic capil- 

 laries being thus permitted, that part of the circulation also is relieved, 

 the lividity and coldness of the surface of the body are removed, and 

 simultaneously, the vigor of the left side of the heart being increased, 

 the flow of properly oxygenated blood throughout the whole system, 

 and life itself, is restored. The action of the air upon the blood in 

 the capillaries of the skin, may slightly assist in these favorable 

 changes ; for the lividity of the skin sometimes diminishes, even when 

 life is not restored. 



It has been found by Dr. Richardson, that artificial respiration, by 

 direct inflation of the lungs of animals, fails to restore the pulmonary 

 capillary circulation, if the beats of the heart have actually ceased, an 

 event which usually occurs after five minutes. Insufflation of the lungs 

 with hot air, is more stimulating to the heart, but yet not adequate to 

 restore the pulmonary blood current. The employment even of oxy- 

 gen or ozone, mixed with the air, is useless, unless the heart is still 

 acting. Galvanism will revive the respiratory movements, but, unless 

 the heart ia still beating, it fails to re-establish the motion of the blood 

 through the lungs. In short, if once the blood-current in the pulmonary 

 artery and its branches be interrupted, the blood corpuscles in the small 

 vessels speedily coalesce, and then the increasingly feebler contractions 

 of the heart merely propel blood into the trunk of the pulmonary 

 artery, but not through the lungs. Artificial respiration by insufflation, 

 or even by Silvester's method, must not be attempted, or continued, 

 when the feeblest natural respiratory movements are discernible. The 

 introduction of air into the lungs must then be very gentle ; the tem- 

 perature of the air should, if possible, be as high as 120, and never 

 below 60. Galvanism, being exhaustive of, as well as stimulating to 

 the respiratory muscles, should either be employed for a limited time, 

 or should be perhaps avoided. Certain experiments, on'- what Dr. 

 Richardson terms artificial circulation, encourage him to hope, that 

 means may ultimately be found of restoring life, if the blood is not ac- 

 tually coagulated, an event which does not usually take place before 

 twenty minutes, and may not do so within an hour, in unopened and 

 unexposed bloodvessels. Injections of oxygen into the circulation, or 

 of peroxide of hydrogen into the trachea, may excite the heart or mus- 





