150 REPORT — 1872. 



In the mean time it is the function and duty of all who have the means and avo 

 interested in scientific progress, and especially of us, the members of this Section of 

 the British Association, to afford such aid as we can to those who, supported by 

 their own enthusiasm ratlier than by the prospect of honour or emolumeutj are 

 willing to devote their lives to physiological and anatomical researches. 



On the Arrangement and Nomenclature of the Lobes of the Liver in Mammalia, 

 Bij Prof. W. H. Flower, F.E.S. 



The descriptions of the livers of ■\'arious animals to be met with in treatises or 

 memoirs on comparative anatomj' are generally verj' difficult to understand for 

 want of a uniform system of nomenclature. The present communication, which 

 endeavours to supply such a system (and was illustrated at the Meetiui^ by a large 

 series of coloured diagrams), is based upon an examination of the condition of the 

 organ in examples of every important subdivision of the class. The difficulty 

 usually met with, arises from the circumstance of the liver being divided some- 

 times, as in man, ruminants, and the cetacea, into two main lobes, which have 

 alvv^ays been called respectively right and left ; and in other cases, as the lower 

 monkeys, carnivora, rodentia, &c., into a larger number of lobes. Among the 

 latter, the primarj' division usually appears at first sight to be tripartite, the whole 

 organ consisting of a middle, called " cystic " or " suspensory " lobe, and two 

 lateral lobes, called respectively right and left lobes. This introduces confusion in 

 describing livers by the same terms throughout the whole series of mammals, as 

 the right and left lobes of the monkey or dog, for instance, do not correspond with 

 the parts designated by the same names in man and the sheep. There are, more- 

 over, conditions in which neither the bipartite nor the tripartite system of nomen- 

 clature will answer, whicJi we should have considerable difficidty in describing 

 without some more general system. 



It appears desirable to consider all livers as primarily divided by the iimbilical 

 vein into two segments, right and left. This corresponds with its development, 

 and with the condition characteristic of the organ in the inferior classes of 

 vertebrates. The position of this division can almost always be recognized in 

 adult animals by the persistence of some traces of the umbilical vein in the form of 

 the round ligament, and by the position of the suspensory ligament. 



"When the two main parts into whicli the liver is thus divided are entire, they 

 may be spoken of as the right and left lobes ; when fissured, as the right and left 

 segments of the liver, reserving the term lobe for the subdivisions. This ^^'ill 

 involve no ambiguity, for the terms right and left lobes \n\\ no longer be used for 

 divisions of the more complex form of liver. 



In the large majority of mammals each segment is further divided by a fissure, 

 more or less deep, extending from the free towards the attached border, which 

 the author proposed to call rir/ht and left lateral fissures. When those are more deeply 

 cut than the umbilical fissure, the organ has that tripartite or trefoil-like form just 

 spoken of, the part between them being the so-called middle, cystic, or suspensory 

 lobe. These terms the author proposed to discontinue, and to institute rij/ht central 

 and left central for the two regions included between the mubilical and the two 

 lateral fissures, and to use riciht lateral and left lateral for the regions l)eyond the 

 lateral fissures. The essentially bipartite character of the organ, and the uni- 

 formity of its construction throughout the class, is thus not lost sight of, even in 

 the most complex forms. 



The left segment of the liver is rarely complicated to any further extent, except 

 in some cases by minor or secondary fissures marking off small lobules, generally 

 inconstant and irregular, and never worthy of any special designation. The piin- 

 cipal differences to be noted depend on the degree of completeness of the lateral 

 fissures (which sometimes extend quite across the hepatic tissue, completelysevering 

 the left lateral lobe) and the relative size of the two lobes. 



On the other hand, the right segment is usually more complex. The right 

 lateral fissru'e when fully developed passes into the right extremity of the portal 



