156 DISEASES OF HEART. 



tual strength and both circulations are carried on at the same 

 time. 



The first is the arterial circulation. No function can be dis- 

 charged — life cannot exist, without the presence of arterial blood 

 The left ventricle that contains it contracts, and by the power of 

 that contraction, aided by other means, which the limits of our 

 work will not permit us to describe, the blood is driven through 

 the whole arterial circulation — the capillary vessels and the veins 

 — and returns again to the heart, but to the right ventricle. The 

 other division of this viscus is likewise employed in circulating 

 the blood thus conveyed to it, but is not the same fluid which 

 was contained in the left ventricle It has gradually lost its vita] 

 power. As it has passed along, it has changed from red to black, 

 and from a vital to a poisonous fluid. Ere it can again convey 

 the principle of nutrition, or give to each organ that impulse or 

 stimulus which enables it to discharge its function, it must be 

 materially changed. 



When the right ventricle contracts, and the blood is driven 

 into the lungs, it passes over the gossamer membrane of which 

 the lobules of the lungs have been described as consisting ; the 

 lobules being filled with the air which has descended through the 

 bronchial tubes in the act of inspiration. This delicate mem- 

 brane permits some of the principles of the air to permeate it. 

 The oxygen of the atmosphere attracts and combines with a por- 

 tion of the superabundant carbon of this blood, and the expired 

 air is poisoned with carbonic acid gas. Some of the constituents 

 of the blood attract a portion of the oxygen of the air, and obtain 

 their distinguishing character and properties as arterial blood, and 

 being thus revivified, it passes on over the membrane of the lobes, 

 unites into small and then larger vessels, and at length pours its 

 full stream of arterial blood into the left auricle, thence to ascend 

 into the ventricle, and to be diflused over the frame. 



DISEASES OF THE HEART. 



The best place to examine the beating of the heart is imme- 

 diately behind the elbow, on the left side. The hand applied 

 flat against the ribs will give the number of pulsations. The 

 ear thus applied will enable the practitioner better to ascertain 

 the character of the pulsation. The stethoscope affords an un- 

 certain guide, for it cannot be flatly and evenly applied. 



Pericarditis. — The bag, or outer investing membrane of the 

 heart (" heart case"), is liable to inflammation, in which the 

 efiiised fluid becomes organized, and deposited in layers, in- 

 creasing the thickness of the pericardium, and the difficulty of 

 ♦lift exnansion and contraction of the heart. The only symptomt 



