174 DISEASES OF THE PARENCHYMA OF THE LUNG. 



sides, the temperature sometimes reaches a height greater than any pre- 

 viously attained. 



The pulse, whose frequence in a pneumonia of average severity 

 usually ranges between ninety and a hundred and twenty beats a minute, 

 may in severe cases, where the temperature is very high, attain a fre- 

 quence of a hundred and thirty, or a hundred and fifty or more. While, 

 at the outset of the attack, it usually is large and full, as the malady 

 progresses, it often becomes small and soft. In some cases, this is due 

 to depression of the heart's action, by the high temperature (which 

 always tends to produce asthenia), so that its feeble strokes scarcely 

 overcome the resistance opposed by the aorta to the outflow of the 

 blood. Under these circumstances (upon the principle that the effect 

 is in proportion to the power, and in inverse proportion to the resist- 

 ance), but little blood is expelled from the heart, causing a feeble pulse- 

 wave, and a small pulse. In other, and probably in the majority of 

 cases, it is not the weakness of the cardiac contractions, but the lack of 

 blood in the left ventricle, which causes a deficit in the supply of the 

 aortic system, and renders the pulse small and soft. The left ventricle 

 is imperfectly filled, because afflux of blood to it is obstructed. In an 

 extensive pneumonia, an obstacle to the circulation arises (partly from 

 the inflammatory stasis, partly owing to pressure of the exudation upon 

 the capillaries), which cannot be fully compensated for by acceleration 

 of the capillary circulation in the uninflamed portion of the lung. The 

 consequence is, that too little blood enters the left heart, while the right 

 heart and the veins of the aortic system are overloaded. (Upon cutting 

 into a piece of hepatized lung, but little blood flows from it. The 

 redness in the beginning of hepatization depends upon extravasation. 

 The lack of blood of the inflamed part is most conspicuous in yellow 

 and gray hepatization, and in purulent infiltration.) 



The blueness of the lips and cheeks, which is observed in severe 

 pneumonia, is also dependent upon the disturbance of the pulmonary 

 circulation, and upon impediment to the outflow of blood from the right 

 ventricle, and from the veins of the aortic circulation ; but we have no 

 acceptable explanation of the reddening of the cheek, which often 

 occurs at the side upon which the pneumonia exists. In many in- 

 stances a herpetic eruption develops upon the second or third day upon 

 the lips, more rarely upon the nose, cheeks, or eyelids; and from the 

 frequence of herpes during pneumonia, and its great rarity in abdominal 

 typhus, and other diseases, the appearance of vesicles filled with a cleai 

 liquid may be of diagnostic value hi doubtful cases. 



The headache, by which the invasion of pneumonia is accompanied, 

 ubiially continues throughout the attack. It is generally combined with 

 sleeplessness, or the sleep is ti oubled by dreams ; and, if the patient bo 



