VELOCITY AND PRESSURE OF BLOOD-FLOW. 507 



increase in the pulse pressure, indicating a more effective beat of the 

 heart. So far as the effect on the heart is concerned, the result of a 

 meal is similar to that of muscular exercise, and this reaction may 

 account for the fact, not infrequently observed, that in elderly 

 people whose arteries are rigid an apoplectic stroke may follow a 

 heavy meal. 



The Method of Determining Venous Pressures and Capillary 

 Pressures in Man. A number of methods have been proposed 

 for determining venous pressures in man, the simplest being 

 that described by Gaertner.* It consists simply in raising 

 slowly the arm of the patient until the veins on the back of the 

 hand just disappear. The height above the heart at which this 

 occurs gives the venous pressure in the right auricle, since the 

 vein may be considered as a manometer tube ending in the 

 auricle. In this and in other methods of measuring venous 



Fig. 206. To illustrate the method of measuring venous pressure: H, The back of 

 the hand in which a single vein is represented; B, the circular rubber bag with central 

 opening, and with a tube, T, which leads to the pump and the manometer; G, glass plate 

 held over the rubber bag. The bag, B, is blown up by pressure through the tube T until 

 the vein is collapsed. The pressure at which this occurs, or the pressure at which the 

 vein reappears as the bag is allowed to empty, gives the pressure within the vein. (von 

 Recklinghausen.) 



pressures, and the same is true, of course, of arterial and capillary 

 pressures, there must be some agreement as to what constitutes 

 the heart-level, since the highest and lowest points of the heart 

 when the individual is standing or sitting may differ by as much 

 as 15 centimeters, von Recklinghausen proposes the level 

 made by a dorsoventral line drawn from the bottom of the 

 sternum (costal angle) to the spinal column. This authorf has 

 devised a simple apparatus for determining venous and capillary 

 pressures, the principle of which is shown by the schema repre- 

 sented in Fig. 206. 



A circular bag of thin rubber with a diameter of about 5j cm. is provided 

 with a central opening of 2 cm. The bag is connected with a pump so that 

 it can be blown up, and the degree of pressure exerted is measured by an 

 attached manometer. This bag, moistened with glycerine, is laid upon a 

 vein, as represented in the diagram. It is covered by a glass plate held firmly 

 in position and the bag is then blown up until the vein disappears; the pressure 

 at which this happens is shown by the manometer and marks the pressure 



* "Muench. mediz. Wochenschrif t, " 1903, 1904. 



t Von Recklinghausen, "Archiv f. exper. Pathol. u. Pharmakol.," 55, 470, 

 190o. 



