250 ANIMAL PHYSIOLOGY. 
distinct, and the reverse when the pressure is low, as after 
hemorrhages. These features are especially marked in the 
Peg Sel 
ARANETA RSA AA 
»——— 
Fig. 223.—Normal pulse-curve in the aorta from the dog. 
dicrotic pulse of fever, etc., when the blood-pressure is low and 
may be recognized even by the hand. The anacrotic crests 
and notches are abnormal, and probably 
- due to excessive rigidity of the arteries, 
Certain it is that, without any change 
in the heart-beat, changes in the tracings 
may arise, owing to modifications in the 
periphery of the vascular system. We do 
not propose to discuss the above-men- 
Fra. § Sate a tioned views of the causation of the minor 
the ascending aortaina features of the tracings in detail, about 
which the greatest differences of opinion 
still prevail. Even if all the characteristics of an arterial 
tracing could be ob- 
tained from an arti- 
ficial schema, it 
would not follow f 
that the conditions 
in each case were 
the same; in fact, ———> 
as we view the mat- 
ter, it would be all 
but impossible that “™ 
such should be the ara 
case. 
Rubber tubes are @ 
not comparable to a ae 
arteries 5 and ESPC- Fig, 225.—Influence of changes in the pressure applied to 
cially not to artery. fs Sete ot te ree eae rer oe 
oles and capillaries fous Fgh ae Ean aerial promure of fos 70 mn. 
Bearing in mind the 
peculiar nature of the blood-corpuscles; their relation to the 
walls of the vessels in which they flow; the relation of the 
