DEVELOPMENT OF LOBULE OF PIG’S LIVER ol3 
Usually, however, before the time the connective tissue sep- 
tum is complete, the new lobules themselves have begun to 
divide, thus giving rise to what Kiernan (’33) has described 
as compound lobules. That the compound lobules of the adult 
are, as I have stated before (’18 a), incompletely divided lobules 
due to incompletely developed connective tissue septa is quite 
apparent; they are similar in every detail to those found in 
the developmental stages. 
Compound lobules have also been described and modeled 
by Debeyre (10) who states that in the pig as well as in other 
mammals they are more numerous than the single lobules. 
“Le petit lobule classique, isolable, existe, mais il est presque 
exceptionnel.”’ 
While I am able to confirm Debeyre in that the compound 
lobules of the pig’s liver are numerous, I have not found the 
single lobule to be exceptional. If blocks of pig’s liver are treated 
with 50 per cent to 75 per cent hydrochlorie acid (Johnson,’18), 
the connective-tissue septa are destroyed and the lobules fall 
apart. The compound lobules, joined together by liver paren- 
chyma, are preserved intact. Examination of the lobules 
under the binocular microscope shows that many of the lobules 
are single. It is true that the compound lobules may be torn 
into their component parts, but this does not happen if they 
are handled carefully. If the maceration is allowed to proceed 
to the proper degree, the lobules separate from one another 
on a very slight amount of shaking. The compound lobules 
ean be divided only upon rough handling. From a number 
of such preparations I have observed that the compound lobules 
vary greatly in number, size, and number of component parts 
in the livers of different adult pigs. 
In addition to the above-described process of division, 
there is another which frequently takes place. Instead of the 
distal end of the hepatic vein bifurcating, a new branch is given 
off from its side. The new branch, as shown in figure 10, enters 
a portion of the lobule. As it gradually becomes larger and 
longer a cleavage takes place in the lobule in a-similar manner 
to that described above. The cleavage divides the original 
