ANOCIATION 259 



operations on the thyroid in cases of exophthalmic 

 goiter, thus preventing excessive activation with the 

 resultant excessive acid by-products. 



Postoperative Pneumonia 



Many theories have been advanced to account for the 

 more frequent occurrence of pneumonia after operations 

 in the upper abdomen, than after operations in the 

 lower abdomen, on the back or on the extremities. 

 That pneumonia is not due to ether alone is proved by 

 its occurrence after operations under local anesthesia. 

 That it is not due to infection alone is shown by the 

 fact that it occurs as frequently in connection with un- 

 infected as with infected wounds. That it is not due 

 to emboli or thrombosis alone is evident from the fact 

 that superficial wounds are rarely followed by pneu- 

 monia. 



The clue to the real cause is found in a comparison 

 of the postoperative behavior of patients operated upon 

 under anociation with those operated upon without that 

 protection. After the nocuous operation the wound is 

 tender. As the upper abdominal muscles have spe- 

 cially important respiratory functions, in each respiratory 

 movement these powerful muscles pull on the stitches 

 which hold together the divided wall. The exquisite 

 pain produced by this respiratory pull causes the inhi- 

 bition of the muscular contractions on the side of the 

 incision, or on both sides if the wound be median. As 

 a result, the excursion of the lower chest wall is dimin- 

 ished, so that the lower lobes of the lungs cannot be 

 filled completely. That a lessened exchange of air in 

 the lower lobes predisposes to pneumonia is suggested 



