9 
234 A Study of the Structural Unit of the Liver 
area has increased in extent. A larger quantity of blood will flow into 
it, therefore, and this will involve a corresponding increase in the total 
resistance to the stream within the enlarged capillary areas. The chain 
of processes described may therefore be repeated until any one link in 
the chain becomes incapable of further increase. 
ie) ean =e SS GS 
ZC po 
Y BESS 
Qo 
oe 
OOS 
ROLBD 
Ni 
0 Ox 
S 60) 
Ew 
Dn SLO, 
Fic. 3. Blood-vessels from the area vasculosa after fifty-seven hours’ in- 
cubation. The same part as in Fig. 2. S, peripheral end of the primitive 
aorta; a, b, c, the selected channels of entrance to capillary network; V, V, V, 
venous exit of latter; d, d, d, the beginning of the second capillary network. 
x 25. After Thoma. 
“Tf we consider that this chain of processes is constantly repeated 
within short spaces of time, and that at each time only a slight alteration 
of the previously existing relations is produced, we may form a fairly 
accurate conception of the mode of growth of the vascular system. 
The details of this will not be considered here. If, however, we apply 
the above principles to any organ whatever which has a longer existence 
