Hamajlatks. 47 
Velocity would be greatly increafed, by pac- 
ing thro’ that narrower Defilec ; but the Ar- 
teries continually fending off innumerable 
Branches, the Sum of whofe Orifices are con- 
fidetably larger than the main Stems, hence 
the Velocity of the Blood mufl: be proportio- 
nably rebated. So that as Dr. James Keill in 
his Tentamina Medico-Phyjicay p. ^6. has eC- 
timated it, the Velocity of the Blood at the 
Heart, would be to its Velocity in an evane- 
fcent Artery as 5233 to i, if it had a free 
unimbarrafled Courfe thro’ thofe capillary Ar- 
teries. And fince the Velocity at its palling 
from the Heart to the Aorta is at the rate of 
149.2 Feet in a Minute, taking one third of 
that, viz> 49.75 for its continued equable 
Velocity, according to Dr. Keilh Eftimate ic 
would move but 0.0095th part of a Foot or 
0.085 Inch in a Minute, in the evanefcenc 
Arteries in that time. 
24. This would be its Velocity there, if 
the Blood had as free and unimbarrafled a 
Courfe thro’ the finer capillary Arteries, as it 
has thro* their larger Ramifications. But by 
the following Experiment it is found, that the 
principal Obftruftion to the Progrefs of the 
arterial Blood is in the capillary Arteries. 
Experj- 
