i8 4 THE POPULAR SCIENCE MONTHLY. 



inflammation. The former are diseases which tend to widen the val- 

 vular apertures, and to dilate the right side of the heart ; the latter 

 are diseases which tend to contract the valvular apertures, and to in- 

 crease the size and bulk of the left side of the heart. 



Disease of the right side of the heart is essentially passive and 

 secondary in its character ; disease of the left side of the heart is es- 

 sentially active and primary in its character. I speak now of disease 

 when it occurs, not when it has existed for some time. Active inflam- 

 mation of the left chambers of the heart arises ; it progresses to a cer- 

 tain extent ; treatment subdues it ; the patient recovers ; but a certain 

 amount of damage is left behind. Years pass on ; the patient during 

 this time appears none the worse for his previous illness ; but at length 

 pulmonary symptoms suddenly manifest themselves, and then it is that 

 the physician discovers that the left side of the heart is permanently 

 damaged, and that the present condition of the lungs is traceable to 

 this cause. 



In this instance the mischief in the heart inducing: this condition of 

 the lungs is not, strictly speaking, active. The first step of the cardiac 

 disease was active ; but the second step was chronic. Bit by bit in- 

 crement by increment after the patient's apparent recovery from the 

 primary attack, is the valvular lesion left by such attack added to, not 

 perhaps constantly, but intermittingly, until at length the aggregate 

 increments of addition so hamper, oppress, obstruct, and distort the 

 mitral, or the mitral and aortic valves, that secondary consequences 

 begin to follow. 



Why are the affections of the two sides of the heart essentially dif- 

 ferent in their nature ? Why do those of the left side of the heart 

 point to an inflammatory origin ; those of the right side of the heart, 

 with but few exceptions, to a non-inflammatory origin ? There must 

 be some cause for this difference. What is it ? The reason is found 

 in the difference which exists between the constitution of the blood 

 which reaches the left side of the heart from the lungs, and that which 

 reaches the right side of the heart from the general system. The 

 blood reaching the left side of the heart from the lungs has been 

 replenished with all the elements necessary for the growth of the tis- 

 sues ; it has been purified, renovated, and vivified by its oxygenation 

 in the lungs, and it is thus rendered in the highest degree stimulating 

 to the left heart. The blood reaching the right side of the heart from 

 the general system has been deprived, by the requirements of growth, 

 of the chief portion of its nutrient materials ; it has been fouled by the 

 debris of tissue-waste ; it has been further poisoned by its impregna- 

 tion with carbonic-acid gas : it is therefore a depressant, rather than a 

 healthy excitant, to the right heart. True, it brings with it to the 

 chambers of the right heart the products of the digestion of food ; but 

 what are they, either as nutrients or excitants, when they reach that 

 point ? They are no more than inert, unusable, passive elements. Not 



