124: DISEASES OF THE PARENCHYMA OF THE LUNG. 



of explanation. In valvular affections of the left heart the pulmonary 

 circulation is surcharged with blood, while the quantity of blood in the 

 aortic system is abnormally small. On the other hand, in emphysema 

 where many of the pulmonary capillaries have perished, and in con- 

 genital malformation of the right heart where the ventricles are usually 

 ill developed, or have their orifices contracted, it is the greater circular 

 tion which is overloaded, and the smaller which contains too little 

 blood. 



This obstructive engorgement of the great veins extends also to the 

 thoracic duct. When the subclavian vein is filled to distention, the flow 

 of lymph and chyle must encounter a resistance equal to that opposed to 

 the current of any other vessel which empties into the subclavian. 

 Now, if lymph be the source of the fibrin in the blood, we see, upon 

 simply physical grounds, why the blood of emphysematous patients is 

 poor in fibrin, why the " venous crasis prevents hyperinosis and increase 

 of fibrin." Restricted afflux of chyle must, moreover, prejudice nutri- 

 tion both of the blood and of the entire organism. It is one of several 

 causes which contribute to the general emaciation and to the premature 

 marasmus of emphysematous persons ; perhaps, too, it may account for 

 the lack of albumen in the serum of the blood, which produces a ten- 

 dency to the establishment of dropsical symptoms. 



As soon as the circulatory derangement ceases to be properly com- 

 pensated for, symptoms of insufficient afflux of blood into the left side 

 of the heart add to those of venous engorgement. Incomplete filling 

 of the left heart produces a small pulse, a pallid complexion, and finally 

 distinct diminution in the urine, as the amount of the urine depends 

 chiefly upon the filling of the renal arteries and glomeruli of the mal- 

 pighian capsules. The scantily secreted urine is concentrated, thick, and 

 dark ; the urates, which require a great deal of water for their solution, 

 precipitate with readiness, in the form of a brickdust-like sediment. 

 Precipitation of the urates is not due to concentration of the urine alone, 

 nor to a relative increase in the quantity of the salts, but it may also 

 depend upon their absolute increase, upon the formation of uric acid 

 at the expense of the urea, the scanty supply of oxygen being insuf- 

 ficient to oxydize the nitrogenous products of the transmutation of tissue 

 BO as to produce urea, but only to such a lower degree as to give uric 

 acid. 



All other symptoms attributed to emphysema belong to its compli- 

 cations. The cough is a symptom of the chronic bronchitis, and often 

 disappears altogether during the summer, while the emphysema con- 

 tinues as usual. In by no means all cases does physical examination 

 give any fixed basis for the recognition of emphysema, and, when of 

 small extent, its existence cannot ever be physically proved. 



