232 Experimentation upon Animals 



an inch square. The skin is then washed with a disinfecting solu- 

 tion, an incision one and a half inches long made through the skin 

 and superficial fascia in the middle Une of the neck, the tissues care- 

 fully separated, the deep fascia cautiously opened, the tissues sepa- 

 rated with the point of the forceps and a grooved director, the 

 sheath of the vessels opened, and the artery completely separated 

 from its surroimding tissues for a distance of at least an inch. A 

 ligature is now tightly tied about the artery at the distal end of ex- 

 posure, and a ligature placed in position and loosely looped ready to 

 tie about the proximal end. A tube with a sharp lateral tubulature, 

 as is shown in the illustration, is now made ready by breaking off 



Fig. 74. — Showing the method of taking blood from the carotid artery 



of a rabbit. 



the closed tip, the moistened forefinger of the operator is placed 

 beneath the artery, and the sharp tube inserted (point toward the 

 heart) into the artery, through whose walls it cuts its way easily. 

 The moment the vessel is entered the blood-pressure drives the blood 

 into the tube so that 20 cc. may be collected in about as many 

 seconds. An assistant now ties the artery at its proximal end, the 

 tube is withdrawn, holding it so that the blood does not escape, and 

 the end sealed in a flame. The ends of the ligatures are now cut 

 short and the external wound stitched. The wound usually heals 

 at once, and if subsequent study of the blood is required, the other 

 carotid and the femorals can be similarly employed for obtaining it. 

 Many experimenters now adopt a more simple method of obtaining 

 the blood from guinea-pigs, and that is by introducing a needle 

 through the chest wall into the heart and withdrawing the blood into 



