Franklin P. Mall .- 247 
both hepatic and portal veins is to be controlled by the volume of the 
structural unit. In general it is found that there are two terminal 
portal veins for one terminal hepatic; the former are always smaller and 
more slender, while the latter are tortuous and end abruptly. 
It is not necessary for the blood to pass through vessels of all orders 
in order to reach the capillaries, for often veins of a given order have 
Fic. 5. Corrosion specimen of the portal tree in man. The injection was 
made with the liver in position. G@ bl, gall bladder; /t, ligamentum teres; 
ls. ligamentum suspensorium; Ci, vena cava inferior; tr. v. p. trunk of the 
vena portae; r. ha, l. ha, right and left main branches; ru, recessus um- 
bilicalis; r. arc, ramus arcuatus; r. desc, ramus descendens; r. asc, ramus 
ascendens. After Rex. 
vessels of three following orders arising side by side from the main 
trunk. Thus, branches of the first order have arising from them vessels 
of the-second, third and fourth orders, and branches of the second order 
have arising from them veins of the third, fourth and fifth orders. The 
main trunk has branches as small as the third order arising from it, and 
these in turn have branches as low as the sixth order arising from them. 
Thus in special cases blood may pass directly from the main trunk into 
