BLOOD PRESSURE 371 



must be attributed to diverse external and internal influences. Fluc- 

 tuations of 50 to 60 mm. Hg are not uncommon. Meals possess an aug- 

 mentor effect, in spite of the fact that the portal blood-vessels receive 

 large quantities of blood during the periods of digestion. ^ Janeway's 

 charts show a rise of 5 mm. Hg in the systolic and a fall of 5 mm. Hg 

 in the diastolic pressure after the midday and evening meals. To 

 this augmentor effect, as well as to the sudden reflex vasoconstrictor 

 reaction, must be attributed the peculiar cerebral symptoms which 

 are frequently experienced after too hearty a meal. Apoplectic seiz- 

 ures are prone to occur under these circumstances, provided, of course, 

 that the arteries have been rendered brittle by calcareous infiltration. 

 Deep and forced breathing increases the pressure. It is decreased 

 during menstruation,^ but rises during pregnancy,^ especially during 

 its later stages, and shows a most decided increase during labor in 

 consequence of the pronounced sensory stimulations and musculo- 

 motor efforts. Baths at the temperature of the body have no marked 

 effect, but cold baths (30-35° C.) produce a rise in the systolic pressure. 

 Hot baths (40° C. and over) generally possess a similar effect on account 

 of the resulting increase in the frequency of the heart.* Water con- 

 taining carbon dioxid, acts augmentatively, but only if the cardiac 

 energy has not been diminished. 



As far as the influence of muscular exercise is concerned, the more 

 recent determinations which have been made with the help of the in- 

 direct method, seem to fully bear out the results obtained in horses 

 and dogs at an earlier date by means of the direct method.^ Thus, 

 HilP has shown that on moving about, the pressure rises from 10 to 

 20 mm. above that shown when at rest or asleep. Furthermore, the 

 experiments of Edgecomb and Bain,^ Masing,^ Karrenstein,^Lowsley,^^ 

 and others have demonstrated that the effect of muscular work depends 

 entirely upon its severity. In all forms of it, an initial rise results, 

 which is retained for a time if the muscular efforts have been slight, 

 or is displaced by a fall, if the exercise has been severe or of long 

 duration. A moderate fall in arterial pressure, however, is not an 

 uncommon symptom of moderate muscular work. 



1 Gumprecht, Zeitschr. fiirklin. Med., xxxix, 1900; Jellinek, ibid., xxxix, 1900; 

 Somerfeld, Dissertation, Erlangen, 1901, and Janeway, Clin. Study of Blood 

 Pressure, New York, 1904. 



2 Federn, Wien. klin. Wochenschr., xv, 1912. 



^ Wiessner, Deutsch. Arch, fiir klin. Med., 1907, and O. Miiller, Kongr. fur 

 Inn. Med., 1902. 



* Strasburger, Zeitschrift fiir klin. Med., liv, 1904, 373. 



^ Zuntz and Hagemann, Deutsch. med. Wochenschr., 1892, and Kaufmann^ 

 Archiv de physiol., ser. 51t. 4. 



« Jour, of Physiol., xxii, 1898, Proc. 26. 



7 Ibid., xxiv, 1899, 48. 



8 Deutsch. Arch, fiir klin. Med., Ixxiv, 1902. 



9 Zeitschr. fur klin. Med., i, 1903. 



^° Am. Jour, of Physiol., xxvii, 1911, 446. 



