THE BLOOD-PRESSURE IN THE ARTERIES. 165 



compressed and pulsation beyond the point of compression is abolished. In the 

 temporal artery the pressure is from 80 to 1 10 mm. of mercury. 



Both of the foregoing methods not only demonstrate the blood-pressure within 

 the arteries, but the pressure exerted by the cushion must exceed the arterial 

 pressure to a degree sufficient to compress the empty artery (which in itself repre- 

 sents a gaping tube). As compared with the blood-pressure, however, the resist- 

 ance of the artery is extremely slight, being only 4 mm. of mercury, although 

 naturally greater in cases of arteriosclerosis. In the same way the resistance 

 offered by the soft parts superposed upon the artery must also be overcome and 

 in individuals of firm fiber with an abundance of fat this resistance is not incon- 

 siderable. In this way v. Basch found in adults a pressure of from 135 to 165 

 mm. of mercury in the radial artery; from 80 to no mm. in the superficial tem- 

 poral. Federn thinks it is lower, namely from 80 to 100 mm. of mercury. 



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

 superficial temporal it was found to be 97 mm. between 2 and 3 years of age, 

 and 113 mm. of mercury between 12 and 13 years of age. The blood-pressure 

 rises immediately after exercise; it is higher in the recumbent than in the sitting 

 posture, and in the latter than in the erect posture. After a cold, as well as after 

 a hot, bath the blood-pressure is at first raised and the flow of urine is increased. 



Hurthle employs the plethysmograph (Fig. 73) in the following manner for 

 measuring blood-pressure. The glass cylinder communicates with a mercurial 

 manometer. The forearm, first rendered bloodless by firmly bandaging it, is 

 introduced into a cylinder containing water and closed in hermetically. When 

 the blood is allowed to flow freely into the arm, the fluid in the cylinder is dis- 

 placed and enters the manometer. The blood continues to flow into the arm until 

 the manometric pressure is equivalent to the blood-pressure. The mean pressure 

 in the arm is said to be about 100 mm. of mercury. Sphygmomanometers have 

 been constructed by Marey and Mosso on similar principles. 



THE BLOOD-PRESSURE IN THE ARTERIES. 



The blood-pressure in the arteries is quite considerable, varying 

 within fairly wide limits. In the larger arteries of large mammals and 

 probably also of man it is between 140 and 160 mm. of mercury. 



Examples : 



Carotid of the horse, i6imm.(Poiseuille). Aorta of the frog, 22-29mm.(Volkmann). 

 212-214 mm. (Volk- Brachial artery of the pike, 35-84 mm. 

 mann) . (Volkmann) . 



dog, 151 mm. (Poiseuille) . Brachial artery in man (after operation) 

 " 130-190 mm. (Lud- 110-120 mm. (Faivre) ; perhaps a 



wig). little too low on account of the 



goat, 118-135 mm. (Volk- traumatism and the disease. 



mann) . 



' ' rabbit , 9 o mm . (Volkmann) . 

 > " chicken, 88-171 mm. (Volk- 



mann) . 



In patients about to be subjected to amputation of the thigh E. Albert, with 

 the aid of a manometer, found the blood-pressure in the anterior tibial artery above 

 the ankle to be between 100 and 160 mm. of mercury. The pulsatory elevation 

 of the column of mercury was from 17 to 20 mm. Coughing caused an increase of 

 between 20 and 30 mm.; firm bandaging of the healthy leg an increase of 15 

 mm.; passive elevation of the body, in consequence of which the length of the 

 hydrostatic column of blood was augmented, an increase of 40 mm. of mercury. 



The pressure in the aorta of large mammals is estimated to be between 200 

 and 250 mm. of mercury. In general, the blood-pressure is lower in large than 

 in small animals because, on account of the greater length of the blood-channels, 

 a greater resistance is to be overcome. In exceedingly young and exceedingly pic 

 animals the pressure is lower than in individuals at the height ^of their vital 



In embryos the arterial pressure is scarcely one-half as great as in the new- 

 born, but the venous pressure is greater. The difference between the arterial 

 and the venous pressure in embryos was found to be scarcely one-half as great 

 as in full-grown animals. 



