ACCIDENTS OF BLOOD-LETTING. 513 



correspondingly profuse hemon-liage, it becomes necessary to have 

 recourse to the direct appHcations of a Hgature. A description 

 of this operation will be made the subject of our chapter on 

 hemostasia. 



5th. Introduction of Air into the Veins. — This is one of the 

 most remarkable of the accidents attending the operation of phle- 

 botomy. The phenomenon has been observed as early as the seven- 

 teenth century, but it was not until 1806 that it was observed and 

 recorded as belonging to the category of casualties connected with 

 the familiar act of blood-letting in an animal. The first author to 

 put the occurrence on record in this connection was Verrier, who 

 reported a case in 1806, and he was soon followed by others with 

 accounts of their experience with the same lesion and operation in 

 human practice. 



There are two principal causes to which this accident can be 

 attributed. One of these may be an unnecessarily large aperture 

 in the vein, but more commonly it follows improper manipulations 

 on the part of the surgeon, particiilarly the irregular pressure 

 made upon the vein during the flow, by many practitioners, who 

 have formed the habit of rubbing the vessel along its length, 

 under the erroneous idea that by this movement they accelerate 

 the bleeding. Again, and perhaps principally, the casualty may 

 be the result of neglecting to close the wound of the skin with 

 the finger below the point from which the current proceeds, before 

 the pressure iipon the vessel is stoj^ped. 



The occurrence is made known by a peculiar gurgling sound, 

 which is made more evident by auscultation of the heart. In the 

 meantime, the animal is attacked by shiverings; the respiration 

 becomes accelerated ; there is a rapid heaving of the flanks ; the 

 body becomes covered with perspiration ; the action of the heart 

 is quickened; the countenance becomes anxious; the animal is 

 seized with convulsions ; falls down and dies, unless by the con- 

 tinuance of the flow through the open vein the air may be carried 

 out through the same channel by which it entered, or unless the 

 quantity has been very minute. As the result of our own study, 

 tested by many experiments, we have become strongly inclined to 

 believe that the quantity of air necessary to produce death must 

 be very large, more, in fact, than a careful operator would allow 

 to enter without attempting to j^revent it. 



The possibHity of the occurrence of this accident may easily 



