USES OF COXTRACTILITY IN VEINS. 541^ 



driven by the powerful left ventricle into the lungs, would be 

 broken, and Uie injurious effects it would otherwise produce be 

 greatly diminished. A similar action may be exerted by the 

 vena cava in cases of tricuspid regurgitation. 



We liave already noticed the persistent contraction which 

 occurred in tlie left jugular vein in Margaret B., at the point 

 where it had been compressed by the collar. This constriction 

 is an indication of one of the properties possessed by veins 

 which is little regarded in considering the mechanism of the 

 circulation — viz., that of contractility. This property they 

 possess to a very great extent, and it is especially remarked in 

 the smaller veins. In these, the walls sometimes approach 

 each other so closely as to completely obstruct the lumen, 

 and altogether prevent the flow of blood through the vein. In 

 them, too, rhythmical pulsations may frequently be noticed. 

 The importance of venoua contractility m reference to the 

 maintenance of the circulation in health and in disease is very 

 great. It is obvious that, if venous radicals contract, they may 

 oppose a resistance to the flow of blood in the capillaries, and 

 by thus increasing the pressure within them may cause more 

 fluid to exude from them into the tissues ; while, on the other 

 hand, a rhythmical contraction may forward the onward pro- 

 gress of the blood in the normal condition, and may prevent 

 some of the injurious effects which are usually noticed in 

 tricuspid regurgitation. Everyone who has studied cases of 

 chronic bronchitis must have been struck with the variety of 

 forms in which the obstruction to the circulation manifests 

 itself in them. In one we find considerable oedema, but no 

 albuminuria; in another, great dyspnoea, with signs of pul- 

 monary oedema, although the legs may be very slightly, or not 

 at all, swollen. In the same case you may see the legs begin to 

 swell, and the pulmonary oedema and dyspnoea at the same time 

 diminish. Such an occurrence I have observed in a patient 

 suffering from chronic bronchitis, and who was apparently at 

 death's door from an acute exacerbation of the disease. This 

 patient was obliged to sit upright in bed, gasping for breatli ; 

 the lips were purple, and all over the lungs there was loud 

 sibilns, and rhonchus, with occasionally coarse mucous niles 



