DEVELOPMENT OF LOBULE OF PIG’S LIVER 323 
tissue is everywhere of the same type, since all its parts are equally 
favored by the circulation, and since, so far as can be determined, 
dividing cells and lobules are uniformly distributed in sections. 
Concerning the growth of the liver, Mall (’06) states: 
In development the liver structure shifts distalwards, successively 
tearing off its capillary connections with the main veins, gradually 
rearranging the architecture of the lobules, often fracturing and 
scattering them. 
Although I agree with Mall that the liver parenchyma shifts 
distalward as the liver grows, I do not believe that the lobules 
become fractured and scattered or that capillary connections are 
torn away. I find no instances of fractured lobules other than 
those undergoing normal binary fission and no instances of the 
scattering of lobules since the lobules maintain their connections 
with the hepatic veins throughout. As for the tearing away of 
capillary connections along the beginning of sublobular veins, it 
seems more probable that such capillaries retract (Clark, ’18), be- 
cause of the decreased flow of blood through them. I believe 
that the shifting of the liver substance peripherally produces no 
destructive changes in the arrangement of its units other than 
that the form of the lobules is altered by the pressure of one lob- 
ule against another due to their manner of growth. 
That the shifting of the liver tissue from the center towards 
the periphery is taking place constantly in the growing liver, 
there can be no doubt. This does not mean, however, that cer- 
tain lobules or groups of lobules are shifting or slipping past one 
another or that they shift along the walls of the blood-vessels. 
In fact, the shifting takes place in such a way that the general 
relations are not at all disturbed. The blood-vessels, ducts, con- 
nective tissue, etc., grow and shift correspondingly with the lob- 
‘ules, and while the liver tissue is shifting from the center toward 
the periphery, it is not to be inferred that the deeper-seated lob- 
ules will eventually come to lie on the surface or even nearer to 
it. On the contrary, they are continuously getting further and 
further away from the periphery for the simple reason that the 
more peripheral lobules are likewise constantly increasing in 
number. 
