LOBULES OF PIG's LIVER 277 



tangular. The deeper ends of these lobules are usually irregu- 

 lar in shape and quite often larger or smaller than the surface 

 ends. Occasionally are to be seen lobules which are markedly 

 pyramidal in shape, the apices of which may be directed either 

 toward or away from the surface of the liver. 



The fact that the lobules of the liver are closely packed solids 

 leads to the question whether or not they resemble any of the 

 regular geometrical solids which fill space. Of such solids, in 

 addition to three, four and six-sided prisms, may be mentioned 

 the tetrahedron, hexahedron, dodekahedron and the tetrakaide- 

 kahedron. The surface lobules, as stated above, tend to be 

 prismatic, but I have found but few of the deeper lobules which 

 approach in form any of the above named geometrical solids. 

 Occasionally, however, one may be found which meets the re- 

 quirements of one of these solids when viewed from one side, 

 but fails when viewed from the other. Several such lobules are 

 shown in figures 1, 2 and 6. If there is any attempt in develop- 

 ment to cut the liver up in similarly shaped units, the adult con- 

 dition does not show it. It should be further pointed out that 

 the lobules in young stages of the pig, amongst them stag-es in 

 which the lobules are just beginning to be marked off from one 

 another, likewise show but very few regularly-shaped lobules. 

 Among the factors which might tend to break up any uniformity 

 in the shape of the lobules may be mentioned the' splitting up of 

 the lobules to form additional ones (Johnson, '17) the unequal 

 growth and size of the variou3 lobules, and the presence of the 

 portal and hepatic canals. 



The statement that the lobules of the pig's liver are com- 

 pletely separated from one another by connective tissue septa is 

 prevalent in anatomical literature. While this is true of the 

 majority of lobules, it will not hold for a large number of them. 

 If a block of liver tissue is macerated in hydrochloric acid there 

 will be seen amongst the completely separated lobules a number 

 which cling together in small clumps of from 2 to 6 lobules each, 

 figures 7, 8 and 10. The individual lobules of these clumps can- 

 not be isolated by shaking or gentle teasing, and a definite tear- 

 ing of the liver parenchjmia is necessary in order to divide them. 



