166 



BLOOD-PRESSURE IN THE ARTERIES. 



sure. He placed a capsule containing fluid upon a pulsating artery, and 

 the capsule communicated with a mercurial manometer. As soon as 

 the pressure within the manometer slightly exceeded that within the 



artery, the artery was 

 compressed so that a 

 sphygmograph placed 

 on a peripheral por- 

 tion of the vessel 

 ceased to beat. Both 

 arrangements, how- 

 ever, do not give the 

 exact pressure within 

 the artery, they only 

 indicate the pressure 

 which is required to 

 compress the artery 

 and the overlying soft 

 parts. The pressure 

 required to compress 

 the arterial walls, how- 

 ever, is very small 

 compared with the 

 blood-pressure. It is 

 only 4 mm. Hg. v. Basch estimated the pressure in the radial artery 

 of a healthy man to be 135-165 millimetres of mercury. 



In children the blood-pressure increases with age, height, and weight. In the 

 superficial temporal artery from 2-3 years, it is = 97 mm. ; from 12-13 years, 113 

 mm. Hg. (A. Eckert, c. 100). The blood-pressure is raised immediately after- 

 bodily movements ; it is higher when a person is in the horizontal position than 

 when sitting, and in sitting than in standing (Friedmann). After a cold as well 

 as after a warm bath (L. Lehmann), the first effect is an increase of blood - 

 pressure and of the quantity of urine (Grefberg). 



Fig. 75. 

 Fick's Spring-manometer, as improved by Hering. 



85. Blood-Pressure in the Arteries, 



The following results have been obtained by experiment on systemic 

 arteries: 



(a.) Mean Blood-Pressure. The blood-pressure is very considerable, 

 varying within pretty wide limits; in the large arteries of large 

 mammals, and perhaps in man it is = 140 - 160 millimetres (5*4 to 6 -4 

 inches) of a mercurial column. 



The following results have been obtained, those marked thus * by Poiseuille, 

 and those + by Volkmann : 



