34 



MORPHOLOGY OF THE 



appears much larger than is usual, and occupies the normal 

 position and relations of the undeveloped caudate lobe. This 

 is perhaps the most striking example of this phenomenon, 

 and seems to corroborate the theory that the liver develops 

 in the direction of least resistance. The cause of resistance 

 is, of course, often quite unknown. 



There is no difficulty whatever in the identification of 

 the liver lobes in a dissected embryo of 14 mm., and yet the 

 proportion that these lobes bear to each other in the embryo 

 is very different from their proportions in the adult. We 

 have already seen that in the latter the right lateral is a very 

 much smaller lobe than the right central. On the other 



s 



Fig. 20. 



The caudal surface of liver and stomach of a 50 mm. cat embryo. (Enlarged 

 5.3 diameters.) r. c, right central lobe, z., intestinal groove. fZ., duodenum. 

 r. L, right lateral lobe, c, caudate lobe, .s., Spigelian lobe. I. left lateral 

 lol)e. 7)., pylorus. /., fundus. 



hand, in the embryo, it is one of the largest of all the lobes. 

 In the adult, the Spigelian lobe seems to be of little impor- 

 tance, and yet, during development, it plays a most promi- 

 nent part in the position of the stomach. The individual 

 lobes not only differ in their proportions in the embryo and 

 in the adult, but they also differ in the direct influence they 

 exert upon the adult position of certain abdominal organs. 

 Fig. 20 shows the relation of the stomach and duode- 



