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rior. The upper current of blood enter¬ 
ing into the fuperior part of the finus, and 
meeting with this barrier or ifle, in Head 
of delcending to the bottom of the iinus, 
is directed obliquely (for the ifle here pre- 
ients a convex furface) againfl the upper 
part of the auricle, but this cavit) being 
likewife mufcular and irritable, at the 
inftant the blood flrikes againfl: it, con¬ 
trails violently, forces it againfl: the fupe¬ 
rior cava, and makes it mount to the head. 
This blood is obliged by its gravity to fall 
again into the auricle, but is again chafed 
upwards, fo that it afcends and defcends al¬ 
ternatively, combated by the fame powers 
till a new infpiration takes place. 
By the infpiration, the air enters the 
thorax, the diaphragm defcends towards 
the abdomen from behind forwards, com- 
prefles the extremity of the inferior cava, 
and clofes its extreme orifice which opens 
in the bottom of the right finus. The 
euflachian 
