BLOOD PRESSURE 365 



Horse 180 mm. Hg 



Calf. 160 mm. Hg 



Sheep 160 mm. Hg 



Dog 140 mm. Hg 



Goat 130 mm. Hg 



Cat 110 mm. Hg 



Rabbit 100 mm. Hg 



Guinea-pig 85 mm. Hg 



As the fluctuations even among animals of the same species are very 

 considerable, it is not apparent that the size of the animal bears a 

 direct relationship to the pressure. It is also noted that the pressures 

 among animals of different species vary so widely that they overlap. 

 In spite of this divergency, however, there seems to be a definite tendency 

 on the part of animals of the same group to preserve a certain height 

 of blood pressure. The cold-blooded animals show much lower values 

 than the mammals. The following table may be of interest: 



Cephalopods 25-80 mm. Hgi 



Fishes (torpedo) 25 mm. Hg^ 



Amphibia: 



Grassfrog 29-40 mm. Hg^ 



Bullfrog 22-26 mm. Hg* 



Reptilia : 



Crocodile 30-50 mm. HgS 



Turtles 25-35 mm. Hg^ 



Concerning the arterial pressure it may be stated that it diminishes 

 gradually in the direction from the heart toward the periphery, but 

 the decrease is slight, because the pressure in the distalmost arteries 

 is only a few millimeters below that prevailing in the aorta. This fact 

 implies that the blood does not encounter a considerable resistance 

 during its journey to the arterioles. Volkmann, for example, found 

 the pressure in the carotid arteries of two calves to be 116.3 and 165.5 

 mm. Hg, respectively, while the pressure in the metatarsal arteries 

 amounted as yet to 89.3 and 146.0 mm. Hg. For the dog Fick^ gives the 

 values of 176 mm. Hg for the aorta and 132 mm. Hg for the tibial 

 artery. According to Burton-Opit z , ^ the difference in pressure between 

 the femoral and hepatic arteries of the dog amounts to 4.4 mm. Hg, 

 and between the former and the more distal arteria gastroduodenalis 

 to 10 mm. Hg. The fact that the original pressure is used up much 

 more rapidly in the distalmost branches of the arterial system is 

 indicated by the observations of v. Frey,^ who has furnished the fol- 

 lowing data: 



1 Fuchs, Pfluger's Archiv, 60, 1895, 173. 



2 Schonlein, Bull, scient. de la France, xxvi. 



3 Hofmeister, Pfliiger's Archiv, 44, 1889. 



"^ Burton-Opitz, Am. Jour, of Physiol., vii, 1902, 243. 



5 Edwards, ibid., xxxiii, 1914, 229. 



^ Festschr. zur Iten Sacularf. der Univ. Wiirzburg, i, 1882. 



7 Pfluger's Archiv, cxlvi, 1912, 344. 



8 Festschr. flir B. Schmidt, Leipzig, 1896. 



