ANATOMY AND PHYSIOLOGY 



as before by this " collateral" circulation that has been 

 established. 



The thorough understanding of this collateral cir- 

 culation is one of the most important steps in surgery, 

 for until it was discovered amputations were thought 

 necessary in such cases as those involving the artery 

 supplying a leg or arm, since it was supposed that, the 

 artery being stopped, death of the limb and the sub- 

 sequent necessity for amputation were sure to follow. 

 Hunter solved this problem by a single operation 

 upon a deer, and his practicality as a surgeon led 

 him soon after to apply this knowledge to a certain 

 class of surgical cases in a most revolutionary and 

 satisfactory manner. 



What led to Hunter's far-reaching discovery was his 

 investigation as to the cause of the growth of the ant- 

 lers of the deer. Wishing to ascertain just what part 

 the blood -supply on the opposite sides of the neck 

 played in the process of development, or, perhaps 

 more correctly, to see what effect cutting off the main 

 blood -supply would have, Hunter had one of the deer of 

 Richmond Park caught and tied, while he placed a 

 ligature around one of the carotid arteries one of the 

 two principal arteries that supply the head with blood. 

 He observed that shortly after this the antler (which 

 was only half grown and consequently very vascular) 

 on the side of the obliterated artery became cold to 

 the touch from the lack of warmth-giving blood. 

 There was nothing unexpected in this, and Hunter 

 thought nothing of it until a few days later, when he 

 found, to his surprise, that the antler had become as 

 warm as its fellow, and was apparently increasing in 



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