LECTURE V. 323 



•iXt.) 



part suddenly cracked, and the external 

 elastic matter of the vessel readily yielding, 

 it became distended by the effused injec- 

 tion, into a bulky, but irregular, form. 



Mr. Hunter thought that the great quan- 

 tity of elastic matter which surrounds large 

 arteries was well calculated to prevent that 

 injury to the vessels, which the powerful 

 propulsion of blood by the heart might 

 otherwise occasion. Nay, he observed that 

 the quantity of elastic matter was greatest 

 where it appeared most wanted, that it was 

 greater on the convex part of the arch of 

 the aorta than on the concave. He further 

 observed, that certain arteries which are occa- 

 sionally much elongated, have a far greater 

 share of elasticity in their longitudinal direc- 

 tion than others. The quantity of elastic mat- 

 ter surrounding arteries also gradually dimi- 

 nishes as these tubes recede from the heart, 

 and the impulse of that organ diminishes ; 

 which well known fact corroborates the opi- 

 nions I have just mentioned. The elasticity 

 of the large arteries may also lighten the 

 labour of the heart by the kind of suction 

 it may sometimes occasion. 



