218 GENERAL ANATOMY OF THE SANGTJIFEROUS SYSTEM. 



The researches of the same careful observer has shown, that 

 the right ventricle as well as right auricle,* and right auriculo- 

 ventricular orifice and pulmonary artery, are larger than the 

 corresponding parts of the left side, at all the different stages of 

 life. The mean dimensions in men, taken from many indivi- 

 duals, between the ages of 15 and 79, are 



Left ventricle, length, 34, lines, breadth, 54 lines. 



Right " 37 V " 82 " 



Mean thickness of the ventricles between same ages.f 

 Left at base, 4| lines, middle, 5 lines, near its point, 4 lines. 

 Right " 2 nearly, " 1| " " 1 " 



Mean circumferences of the auriculo-ventricular orifices. 

 Of the left, (between the same ages, 16 to 79,) 45| lines. 

 Of the right, " " 54 " 



Mean circumference of the orifice of the aorta, and pulmo- 

 nary arteries, taken opposite the free border of the sigmoid 

 valves. 



Of the aorta, (between the same ages,) 311 lines. 



Of the pulmonary artery, 32^ " 



The coronary arteries undergo a development in size, exactly 

 in harmony with that of the heart. In the foetus, where the 

 thickness of both ventricles seems equal, there is no difference 

 in the size of the coronary arteries. But as the walls increase 

 in thickness, especially that of the left ventricle, these arteries 

 enlarge, and in particular the left. Boyer, H. Cloquet and 

 others, have fallen into error, in stating that the calibre of the 

 left coronary artery is less than the right. 



* The comparative measurements of the auricles have not been taken. p. 



f The thickness of the septum ventriculorum is about the same as that of 

 the left ventricle, and undergoes the same modifications in respect to age. The 

 columnse carneae are not included in the measurement of the thickness of the 

 ventricle. p. 



$ In the latter ages of life, the aorta increases in its dimensions so as to 

 exceed in circumference at its orifice, the pulmonary artery. This is in all 

 probability owing to the frequency of the morbid alterations of the aorta in old 

 men, in which the middle coat of the vessel loses its elasticity and becomes 

 dilated : while alterations of the pulmonary artery are very rare, even at the 

 most advanced stages of life. p. 



