no 



THE MECHANISM OF THE CIRCULATION. 



employed the arrangement shown in Fig. 74. Into the left auriculo-ven- 

 tricular opening was fastened a tube (R). This tube ended in two branches 

 (P and N). The branch (P) was connected with a pressure bottle (A), and the 

 branch (N) formed an exit tube. A tap was placed in these branches, so that 

 N was opened when P was closed, and P was opened when N was closed. 

 Into the aorta was fixed a long elastic tube ( V). Water was allowed to flow 

 from the pressure bottle through the heart and the aorta. If the tap was 

 now suddenly turned so as to shut P and open N, the pressure sank to zero 

 in the ventricle, and a positive wave appeared in the aortic tube, which was 

 produced by the closure and vibration of the semilunar valves, and not by 

 reflection from the periphery. 



Hoorweg 1 employed a circulatory model in which a current through a 

 Rumkorff coil was completed by the closure of the semilunar valves. The 

 coil sparked on to the smoked paper, and knocked away the soot at the point 

 where the lever style recorded the pulse wave on the drum. The closure of 

 the valves was thus found to take place exactly at the foot of the ascent 

 of the dicrotic wave. 



Hoorweg found that the dicrotic wave appeared at the same 

 interval of time, after the commencement of the primary wave, in 



a dwarf as in a 

 man of tall stature. 

 If the dicrotic wave 

 were of peripheral 

 and reflected origin, 

 it should assuredly 

 have occurred earlier 

 in the dwarf, for in 

 the dwarf the length 

 of artery to be 

 travelled by the re- 

 flected wave would 

 be much smaller. 



Under the in- 

 fluence of inhala- 

 tion of amyl nitrite, 

 the dicrotic w T ave 

 may, it is stated, 

 almost disappear 

 during the maximal 

 effect of the drug 

 (Fig. 75). Those 

 who seek to ex- 

 plain the origin of 

 this wave by the 

 production of re- 

 flected waves suggest 

 that this is so, because the arterioles are so dilated by the drug that 

 little reflection can take place. 2 The evidence in favour of this state- 

 ment is, however, unsatisfactory, and, holding to the central origin of 

 the dicrotic wave, the phenomenon can equally well be explained by 

 the fact that the heart force is diminished while the peripheral resist- 

 ance is lowered, and therefore the back swing of the blood against the 



1 Arch.f. d. ges. PhysioL, Bonn, 1890, Bd. xlvi. S. 143. 



2 v. Kries, loc. cit. 



FIG. 75. Effect of inhalation of amyl nitrite. A, Normal 

 trace ; C, maximal effect of the drug. 



