372 THE MECHANICS OF THE CIRCULATION, HEMODYNAMICS 



While ordinary changes in position^ do not affect the blood pres- 

 sure very materially, extreme changes always induce static effects 

 which the vascular system is at times unable to counteract. Thus, a 

 change from the recumbent to the standing position always leads to a 

 fall in blood pressure, if the tonus of the blood-vessels has been lessened 

 in any way. This condition may be general or local, and is especially 

 prone to involve the blood-vessels of the portal system. As these 

 channels are concerned with the digestion and absorption of foods, 

 they must absorb a large mass of blood, and hence, their static in- 

 fluence must be particularly potent at this time. The effects of vascu- 

 lar relaxation are counteracted in a large measure by a greater ven- 

 tricular discharge, because if a person assumes the erect position, the 

 heart beats more quickly, this increase being proportional to the fall 

 in pressure. If, however, the relaxation is pronounced, the heart is 

 quite unable to effect an adequate compensation and a fall in blood 

 pressure results. Concurrently, it may be concluded that a proper 

 tonicity of the blood-vessels suffices to retain the pressure at its normal 

 level without that the heart need increase its energy. In fact, a person 

 whose vascular system is tonically set, most frequently shows a slight 

 rise on assuming the erect position, because the heart nevertheless 

 tends to increase its frequency by at least a few beats. 



These facts have been employed by Crampton^ in obtaining an index of coiv- 

 dition. A large number of determinations of the blood pressure in normal indi- 

 viduals have been compiled in such a way that their state of physical fitness may 

 be deduced directly from these figures. This is made possible by arranging these 

 values in series in accordance with the alterations in the height of the blood pres- 

 sure and the frequency of the heart which resulted when these persons changed 

 their position from the recumbent to the upright. In accordance with these deter- 

 minations, a person is said to be in a good physical condition if, on assuming the 

 erect position, his systolic pressure diminishes by no more than 12 nor increases by 

 more than 18 mm. Hg. Besides, this change must leave fhe diastolic pressure un- 

 changed, or must not increase it by more than 18 mm. Hg. Quite similarly, the 

 heart must at this time either retain its previous rate or increase its frequency by 

 no more than 40 beats. Greater variations than these are regarded as proving 

 that the vascular system is relaxed and that, therefore, the person is in a poor phys- 

 ical condition. While this test possesses a sound dynamical basis, the results ob- 

 tained should be accepted with great reserve and should not be applied with undue 

 strictness to all persons. 



It should be mentioned that tests of physical fitness have also been devised 

 by Graupner,' and Katzenstein.* The former endeavored to test the functional 

 capacity of the heart by noting the influence of a measured amount of muscular 

 work upon the blood pressure and pulse rate, and the latter, by determining the 

 response of the heart to compression of both iliac arteries. Barach^ has sought to 

 determine the tonic condition of the circulatory system by multiplying the systolic 



1 Shapiro, Med. Jahrb. der K. K. Gesellsch. d. Arzte, 1882; Erlanger and 

 Hooker, Johns Hopkins Hosp. Rep., xii, 1904, and Brocking, Zeitschr. fiir Exp. 

 Path., ix, 1907. 



2 Med. News, 1905. 



^ Berliner klin. Wochenschr., 1902. 



4 Ibid., 1907. 



^ Jour. Am. Med. Assoc, 1914. 



