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into the artery of a living animal, its parietes compress it in every direc- 

 tion ; if the blood is prevented from flowing in it, the canal becomes 

 obliterated by the adhesion of its parietes* and the vessel is converted 

 into a ligamentous cord, such as that formed in the adult, by the remains 

 of the umbilical arteries and veins. This contractility which, during 

 life, is always in action, keeps the arteries, distended by the blood which 

 fills them, of a smaller calibre, than after death. In performing capital 

 operations, especially in the amputation of limbs, I have always found the 

 arteries, whether filled with blood or empty, much smaller than I should 

 have expected from their appearance in the dead body. 



It happens, however, sometimes, that the quantity of blood sent to an 

 organ increases, in consequence of some cause of irritation; the calibre 

 of the arteries of the part, then becomes remarkably enlarged. Thus, 

 the arteries of the uterus, which are very small in its unimpregnated 

 state? acquire, towards the end of pregnancy, a calibre equal to that of 

 the radial artery*, the small arteries which are sent to the mammae, are 

 not in the same condition, as I have had the opportunity of ascertaining 

 in a woman who had been sucking a child for two months before her 

 death; they retained their almost capillary minuteness, which would 

 seem to prove, that the lymphatics are alrme cQnru?merl in bringing to 

 these glands the materials of their secretion. The mammary arteries 

 evidently enlarged in an open cancer of the breast; in cancer of the pe- 

 nis, the blood-vessels likewise become enlarged; hence in removing the 

 penis for that affection, it is absolutely necessary to secure the arteries 

 with ligatures, a precaution which need not be attended to in a case of 

 gangrene. Gangrene is attended with this peculiarity, that the arteries 

 of the mortified parts contract, so as to become obliterated, when their 

 calibre is inconsiderable. 



As the arteries are the canals which convey to all our organs the ma- 

 terials of growth and reparation, they are larger, in proportion, in child- 

 ren, in whom nutrition is more active, and their calibre is always propor- 

 tionate to the natural or morbid developement of organs : hence the de- 

 scending aorta and the iliac arteries are larger in women than in men; 

 hence the right subclavian artery, which conveys blood to the larger and 

 more powerful of the two upper extremities, because being more em ployed, 

 it is larger than the left subclavian. But the effect should not be mistaken 

 for the cause, and it should not be imagined, that the right upper extre- 

 mity owes its superiority to the greater calibre of its artery. In the new- 

 born child, this vessel is not larger than the left subclavin : but the right 

 arm being more frequently employed, the distribution of the fluids takes 

 place more favourably, nutrition is carried on with more energy, it ac- 

 quires more bulk and strength, and therefore the right subclavian artery 

 conveys blood to it by a wider channel. If the left upper extremity 

 were employed in the same manner, and if the right were kept in a state 

 of inaction, the left subclavian would, no doubt, exceed the right. I am 

 warranted by two facts in forming this conjecture. lu dissecting the bo- 

 dies of two men that were left-handed, I observed in the left subclavian 

 arteries, the same proportionate enlargement which is usually met with in 

 the same vessels on the right side. 



* This increase of size in the arteries of the gravid uterus, is a proper growth of parts, 

 not an accidental dilatation* Gadman. 



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