JOSEPH S. JANICKI, DALI J. PATEL, JOHN T. YOUNG AND RAMESH N. VAISHNAV 
577 
Figure 1. — Typical experimental setup to study the left circumflex coronary 
artery and the carotid artery. A — artery; Sc = centimeter scale; W = 
weight; St = string; M = microscope; E = Filar micrometer eyepiece; 
N = hollow metal rod; P = pressure transducer; Res = reservoir; S = 
screw clamp. Insert represents the view of the artery through the micro- 
scope. From Patel, D. J., and Janicki, J. S. Static elastic properties of the 
left coronary circumflex artery and the common carotid artery in dogs. 
Circ. Res. 27:149, 1970. 
screwed into a threaded hole through the cen- 
ter of the proximal plug. The other end of this 
rod was connected to a reservoir (RES) con- 
taining a 6% dextran solution. The reservoir 
was made airtight and connected to an adjust- 
able source of air pressure. Pressure in the 
segment (A), applied via this arrangement, 
was measured using a P-23 Db Statham trans- 
ducer (P). A solid metal plug containing a 
hook was screwed into the distal plug so that 
weights (W) could be hung from it. A centi- 
meter scale (SC) divided in half millimeter 
increments was mounted on a stand behind the 
segment. The length (i.e., the distance be- 
tween the ties coupling the blood vessel to the 
plugs) and mid-segment external diameter of 
the blood vessel segment were measured using 
the microscope system (M) , which was equipped 
with a Bausch and Lomb Filar micrometer 
(12.5x) eyepiece (E). The microscope system 
was mounted on a stand which was adjustable 
in both the horizontal and vertical directions. 
The eyepiece had a moveable hairline con- 
trolled by a vernier knob, which could be used 
to average the vessel diameter over a length of 
approximately 4 mm. 
Figure 2 shows the experimental setup that 
was used to study statically the MDTA, both 
in vivo and in vitro. The setup for the dynamic 
studies was essentially the same except for the 
