224 LECTURE V. 



Mr. Hunter knew, that in cases of hae- 

 morrhage, the arteries would gradually 

 contract upon their diminished contents, 

 to a much smaller calibre than common ; 

 and he measured their areas in the contract- 

 ed state in which they were found in a 

 horse that had been bled to death. H« then 

 distended them, so as to destroy the effect 

 of this vital contraction ; and having suffer- 

 ed them to regain that calibre which their 

 elastic property naturally determines, he 

 again measured their areas, and found that 

 the aorta had contracted, in the first in- 

 stance, to more than one-tenth of its natu- 

 ral diameter, the iliac to one-sixth, and the 

 crural to one-third. He also observed, that 

 arteries corresponding to the radial of the 

 human subject, and others of the same 

 size, were closed. I also think it evident, 

 in the common operations of surgery, that 

 arteries of no inconsiderable magnitude, 

 which have bled vehemently, and in a large 

 stream immediately after their division, 

 very speedily cease to bleed, and remain 

 with their orifices so closed, that they are 

 scarcely discernible. I have seen the radial 

 and ulnar arteries of the human subject. 



