DEVELOPMENT OF LOBULE OF PIG’S LIVER 301 
DEVELOPMENT OF THE CONNECTIVE TISSUE SEPTA 
In stages until nearly birth the liver of the pig shows no indica- 
tions of connective tissue septa. The parenchyma is made up of 
cells not greatly different from those of the adult. The sinu- 
solids, which appear proportionately large, are lined with en- 
dothelial cells. The ‘Gitterfasern’ or ‘reticulum of Mall’ (’96) 
is demonstratable following Bielschowsky’s silver-impregnation 
method, and is also slightly discernible after staining with 
Mallory’s triple connective tissue stain. The branches of the 
hepatic and portal veins interdigitate with one another and 
furnish a means by which hepatic and portal lobules may in 
certain areas be roughly outlined. The large branches of the 
portal veins are readily distinguished from the hepatic, for they 
are accompanied, as in the adult, by branches of the hepatic 
artery and of the bile duct; some of the smaller veins are deter- 
minable only with the aid of serial sections. 
In figure 1 is shown a longitudinal section through a branch 
of the portal vein, taken from the liver of a pig 229-mm. in 
~length. The interdigitation of its branches with those of the 
hepatic vein is clearly shown. Surrounding the larger branches 
of the portal veins, bile ducts, and hepatic arteries is connective 
tissue. Staining with Mallory’s triple connective tissue stain 
clearly demostrates in it the presence of collagen fibrils. Where 
the collagen fibrils are in contact with the parenchyma they 
often send short fibrils into its reticulum. Surrounding the 
hepatic veins there is but a thin layer of connective tissue, 
which, moreover, does not extend out to as small branches as 
does that surrounding the portal veins. The hepatic cells 
are polyhedral in shape, with slightly granular protoplasm and 
distinct chromatic nuclei. They are grouped in strands, but, 
as stated by Theopold, a radial arrangement about the central 
vein is not yet to be found. Here and there are to be seen small 
clusters of nucleated round cells. These cells, which we know 
to be developing blood-cells, were first described by Ko6lliker 
C79), but were thought by Toldt and Zuckerkandl (’75) to be 
young hepatic cells. That Kolliker’s interpretation is correct, 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 25, NO. 3 
