THE PULSATORY VARIATIONS IN BLOOD PRESSURE 393 



in another way, because Henderson^ has shown that the exposure of 

 the heart to a direct pressure of this kind hinders the normal filhng 

 power of this organ and hence, also the flow through the lungs. Cer- 

 tain discrepancies have also been found by Erlanger and Festerling,^ 

 as well as by Snyder, ^ but as a more satisfactory explanation of this 

 phenomenon has not been submitted, it seems bjest to adhere to the 

 analysis previously given. 



The Traube-Hering curves are rhythmic fluctuations in pressure, 

 each of which always embraces a number of respiratory variations.'' 

 They are long, but do not attain a significant height. Their con- 



FiG. 206. — Traube-Hering Curves. 



The time is given in seconds. The smallest pulsations represent the cardiac varia- 

 tions, those of intermediate size the respiratory variations, and the large waves the 

 Traube-Hering variations. 



spicuousness, however, may be increased by curarization, anemia of 

 the bulbar centers and asphyxia. They are commonly ascribed to 

 irradiations of impulses from the excited respiratory center to the 

 vasomotor center. 



Waves of similar character are frequently observed in normal 

 animals and especially in those narcotized with morphin. They are 

 known as the Mayer curves and find their origin in a hyperirritable 

 condition of the vasomotor center. This hyperirritability arises in 

 consequence of bulbar anemia, an increased venosity of the blood, 

 irritations of the central nervous system and the administration of 

 certain drugs, such as digitalis and strophanthus. 



^ Jour, of Physiol., xxxvii, 1908. 



2 Jour, of Exp. Med., xv, 1912. 



' Am. Jour, of Physiol., xxxvi, 1915. 



* Traube, Zentralblatt fur die med. Wissensch., iii, 1865, 882. 



