DEVELOPMENT OF THE LIVER. 879 



specific gravity of the bile is from 1-026 to T030. It has a sweetish bitter taste, and 

 an alkaline reaction. It is a saponaceous compound, containing the following ingre- 

 dients : water, mucus, colouring matters (composed, according to Berzelius, of a 

 yellow substance named cholepyrrhine, a brown substance named bilifulvine, and a 

 green matter or biliverdine), fatty acids, viz., the margaric and oleic, combined with 

 soda, free fat, cholesterine, salts, and, lastly, the most important ingredient of the 

 bile, namely, the proper biliary matter, which consists, according to Strecker and 

 Lehmann, of two " conjugated acids," formed by the union of one acid, the Choleic, 

 in two isomeric forms (the cholic and choloidic acids of some authors) with Glycin 

 and Taurin respectively. Thus the Glycocholic and Taurocholic acids are formed, 

 each of them consisting principally of carbon and hydrogen, but both containing 

 nitrogen, and the latter a considerable quantity of sulphur. They are combined 

 with soda, but are very readily decomposed, giving rise to ammoniacal and other 

 compounds. Of these two acids the glycocholic is the most important. The bile- 

 pigment affords the most characteristic tests for the detection of biliary matter. 



DEVELOPMENT AND FCETAL PECULIARITIES OF THE LIVER. 



The liver begins to be formed at a very early period of foetal life. Both in the 

 mammal, as seen by Bischoff, and in the bird, as Kemak's researches show, it begins 

 in the form of two blind processes from the intestinal tube, immediately beneath the 

 dilatation for the stomach. According to Kemak, these processes involve both the 

 epithelial and the fibrous layers of the intestine; and the fibrous layer, rapidly growing, 

 involves the omphalo-mesenteric vein and forms the outline of the liver : meanwhile 

 the internal structure takes origin by the growth of anastomosing cylinders of cells 

 from the epithelial layer, and of tufts of blood-vessels. 



Fig. 616. EARLY Cox- Fi 616 



DITION OP THE LlVER 

 IN THE CHICK ON THE 



THIRD DAT OP INCU- 

 BATION (from J. M til- 

 ler), i? 



1, the heart, as a sim- 

 ple curved tube ; 2, 2, 

 the intestinal tube ; 3, 

 conical protrusion of the- 

 coat of the commencing 

 intestine, on which tbe 

 blastema of the liver (4) is 

 formed; 5, portion of the 

 layers of the germinal 

 membrane, passing into 

 the yolk-sac. 



The gall-bladder, according to some authors, is developed as a branch or diverticulum 

 from the bile-duct outside the liver; but Meckel describes it as arising in a deep 

 notch in the substance of the gland. It is at first tubular, and then has a rounded 

 form. The alveoli in its interior appear about the sixth month. At the seventh 

 month it first contains bile. In the foetus its direction is more horizontal than in the 

 adult. 



Size. In the human foetus, at the third or fourth week, the liver is said to con- 

 stitute one-half of the weight of the whole body. This proportion gradually decreases 

 as development advances, until at the full period the relative weight of the foetal liver 

 to that of the body is as 1 to 18. 



In early foetal life, the right and left lobes of the liver are of equal, or nearly equal, 

 size. Later, the right preponderates, but not to such an extent as after birth. Imme- 

 diately before birth the relative weight of the left lobe to the right is nearly as 

 1 to 1-6. 



Position. In consequence of the nearly equal size of the two lobes, the position 

 of the foetal liver in the abdomen is more symmetrical than in the adult. In the 

 very young foetus it occupies nearly the whole of the abdominal cavity; and at 



