502 MANUAL OF HISTOLOGY. 



phosphoric acid (Bernard, Frerichs, Bidder, and Schmidt). Sulphocyanide 

 of potassium is not present in the secretion of the pancreas. 



262. 



We come now to the liver, the largest of all the glands connected with 

 the digestive tract in man and the mammalia. Underneath its fibrous 

 investment it presents, even to the unaided eye, a most peculiar appear- 

 ance, owing to its texture. A finer analysis of the latter shows it still 

 more distinctly to be alone among the glands of the body. 



If we carefully examine either the surface or a section of the liver, 

 we notice markings which divide the former into regular fields. This 

 is seen in many mammals very distinctly, but especially so in the pig 

 and also the polar bear. The portions included in these markings are 

 known as the hepatic lobules. They are separated from one another by 

 narrow bands of lighter coloured substance, and are at one time of a 

 dark reddish brown in the central portion, and of a lighter hue nearer 

 their circumference, and at another quite the reverse, appearing light 

 internally and dark externally. These differences depend entirely upon 

 the state of the circulation in the organ. In man this marking is toler- 

 ably easy of recognition in the infant's liver, but is, on the other hand, 

 very indistinct in the adult. The diameter of the lobules may be roughly 

 estimated, on an average, at 9 mm., and about a third more in larger indi- 

 viduals, while, in some cases, they may only measure I'l mm. 



Each of these lobules consists essentially of innumerable gland cells, 

 and an exceedingly complex network of vessels passing among them, and 

 tending all towards one central point, where their confluence forms the 

 commencement or radicle of an hepatic twig, while externally they are 

 bounded by branches of the portal vein and biliary canals. 



The hepatic elements are distinct from one another (fig. 498), and pre- 

 sent great similarity to peptic cells. Their form is more or less irregularly 

 polygonal, owing to their mutual accommodation. In 

 diameter they are, on an average, about 0'0226- 

 O'OISO mm., with extremes up to 0*0282 mm. and 

 down to 0'0113 mm. Their nuclei, which are oval, 

 and contain nucleoli, have a diameter of 0'0056- 

 0-0074 mm. Each cell usually contains one of them 

 (), but may in some cases be possessed of two (b). 

 The substance of which the hepatic cells are composed 

 is of viscid consistence, and presents a greater or less 

 number of fine elementary granules embedded in it. 

 The cells are entirely destitute of membranous cover- 

 ing, and the whole structure, when isolated, is seen to 

 ?i of m a ;T H a?wtt C h C one be possessed of the power of amoeboid motion, very 

 nucleus; 6, a ceil with distinct, though slow (Leuckarf). 



two of the latter. -,-, . , ,, . , v ,. i ,1 ,, p 



Besides these just mentioned, other matters are fre- 

 quently met with in the contents of the hepatic cells, which, when pre- 

 sent in small quantities, may be regarded as normal constituents, while 

 their appearance in greater amount denotes a morbid condition of the 

 cell. These are, in the first place, molecules of a brown or yellowish- 

 brown pigment (biliary colouring matter), and, secondly, fatty globules 

 of varying sizes (fig. 500). The latter, chiefly in the form of very fine 

 fatty molecules, are found normally in sucking animals and children, and 



