AIE IN THE VEINS. 323 



of inspiration is found in an accident which is not infrequent 

 in surgical operations in the lower part of the neck. When 

 the veins in this situation are kept open by a tumor, or by 

 induration of the surrounding tissues, an inspiratory effort 

 has occasionally been followed by the entrance of air into the 

 circulation ; an accident which is liable to lead to the gravest 

 results. This occurs only when a divided vein is kept patu- 

 lous ; and the accident proves both the influence of inspira- 

 tion on liquids in the veins near the chest, and its restriction 

 to the vessels in this particular situation by the flaccidity of 

 their walls. The conditions under which this occurs may be 

 imitated in the lower animals by introducing a tube through 

 the vein into the thorax ; when, with a violent act of inspi- 

 ration, air will be drawn in, and the curious and startling 

 effects upon the circulation may be observed. 



A full discussion of the subject of air in the veins, which 

 is of great pathological interest, does not belong to the domain 

 of physiology. The blood is capable of dissolving a certain 

 quantity of atmospheric air ; and a small quantity, very grad- 

 ually introduced into a vein, can be disposed of in this way. 

 When, however, a considerable quantity suddenly finds its 

 way into the venous system, the patient, or animal, experi- 

 ences a sense of mortal distress, and almost immediately falls 

 into a state of insensibility. A peculiar whistling sound is 

 heard when the air passes in ; and if the ear be applied to the 

 chest, we distinguish the labored efforts of the heart, accom- 

 panied by a loud churning sound. On opening the chest 

 after death, the right cavities of the heart are invariably 

 found distended with air and blood ; the blood being frothy 

 and florid. Generally the left side of the heart is nearly or 

 quite empty. 



The production of death from air in the veins is purely 

 mechanical. The air, finding its way to the right ventricle, 

 is mixed with the blood in the form of minute bubbles, and 

 passed into the pulmonary artery. Once in this vessel, it is 

 impossible for it to pass through the capillaries of the lungs, 



