1 823 .] On the Obstruction of the Blood in the Lungs. 211 



Article XI. 



On the Cause and the Effects of an Obstruction of the Blood in 

 the Lungs. By David Williams, MD. 



(To the Editor of the Annals of Philosophy.) 



Liverpool, Aug. 5, 1823. 



While investigating the effects of the pressure of the atmo- 

 sphere upon the lungs, on its admission into the cavities of the 

 chest, I remarked several appearances that mihtated against 

 every hypothesis advanced, as to the cause of the unequal distri- 

 bution of the blood after death. Reflecting on what I had wit- 

 nessed, and thinking I had observed a phenomenon that had 

 escaped the attention of all the physiologists whose writings I 

 had perused, it encouraged me to a further inquiry. The result 

 of my inquiry has been favourable, as it will, in my opinion, 

 unveil the mystery that envelopes the cause of the comparative 

 vacuity of the system circulating arterial blood post mortem. 

 Before entering into the detail of my research, it will be better 

 to premise the nature of the appearances alluded to. In one of 

 my examinations, after the animal had been suffocated, by 

 making a ligature on the trachea, during the acme of inspi- 

 ration, previous to removing the sternum, I noticed after 

 the action of the heart had ceased, that the blood still flowed 

 into the right auricle and ventricle, and consequently into the 

 pulmonary artery ; and that the propelling agent was so power- 

 ful as to distend the right auricle and ventricle so forcibly after 

 the pericardium was slit open, as to make it doubtful whether 

 they would not burst, yet at the same time the pulmonary veins 

 were comparatively empty. In this instance it was apparent, 

 that the blood was obstructed in its course through the lungs, 

 and that this obstruction was one of the principal causes of the 

 vacuity of the circulating system of the arterial blood. From the 

 distention of the cavities of the right side of the heart, and the 

 gorged state of the cavse, it was evident that no obstacle impeded 

 the return of the blood through the capillaries, from the system 

 at large. In a mechanical point of view, the blood ought to have 

 met with equal impediment in passing through the capillaries, 

 as in passing through the final terminations of the pulmonary 

 artery into the pulmonary veins. Impressed with the compara- 

 tive emptiness of the pulmonary veins, and as no visible subsi- 

 dence of the lungs had taken place, I was at a loss how to 

 assign a cause for the obstruction on a mechanical principle. It 

 .occurred to me that it was probable that the blood (from its 

 vital principle being exhausted in its route through the system, 



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