154 



OPERATIVE TECHNIQUE. 



lightly below the point of operation and caused to appear distinctly. 

 The incision is, as before, at the most prominent point and close to the 

 operator's fingers, because here the vein is more or less fixed. The 

 lancet is thrust inwards and slightly upwards, so as to produce a suffi- 

 ciently large wound, though care must be taken not to absolutely slit 

 open the vessel, as is sometimes done from over-anxiety. It then 

 becomes difficult to stop the flow, and it may be necessary to ligate the 

 vein, in addition to which there is danger of air entering the vessel. The 

 incision should be in the centre line of the vein ; the upper (or posterior) 

 aspect of the vessel must be avoided, as injury to the carotid artery 

 may readily result from incisions in this direction. 



In using the ordinary flean) (Fig. 183) the operator, standing 

 opposite the animal's left shoulder, holds the fleam lightly between 



the index finger and 

 thumb of the left hand, 

 compresses the vein 

 ) with the other fingers, 

 and with a short, smart 

 blow from the blood- 

 stick, or failing this, 

 from the edge of the 

 right hand, drives the 

 fleam into the vein. 

 The fleam must be 

 held exactly at right 

 angles to the skin over 

 the highest prominence 



Fig. i83.-Bleeding with the fleam and blood-stick. ^^ ^^^^ ^^-^^ otherwise 



the vessel will be opened on one side or the instrument will slip 

 past it. 



Dieckerhoff and Caspar have recently recommended a special 

 trocar and cannula for bleeding. As this instrument had been used 

 for some years for intra-\'enous administration of drugs, it occurred to 

 them that it might be equally useful for withdrawing blood, especially 

 where it was desirable to shield the withdrawn blood against con- 

 tamination, as in preparing protective serum. The cannula has the 

 great advantage over the fleam that it can be inserted several times 

 at the same place. In operating, the vein is raised, thq skin 

 divided, and the vein exposed. The operator, standing on the 

 animal's near side, then thrusts the cannula, carrying its shield, 

 steadily into the vein for a distance of three or four inches, when 

 bleeding follows. Some dexterity is required, but the method 



