358 RICHARD E. SCAMMON 



internal yolk sac joining the valvular intestine on the left side of 

 the first turn of the spiral valve. 



Figure 15 shows the gall bladder and hepatic ducts in diagram. 

 The main right and left hepatic ducts join with the ductus chole- 

 dochus obliquely, the left gaining entrance in front of the right. 

 The distance between the ostia of the two ducts varies in different 

 specimens. The left duct after extending a short distance an- 

 teriorly arches far out laterally and there turning backward passes 

 posteriorly in the left lateral lobe. The right duct makes a sharp 

 arch anteriorly and then passes backward into the right lobe. 



The main lateral hepatic ducts give rise to numerous small 

 hepatic tubules and to several larger rami. The former are 

 extremely irregular in form, origin and number, but the latter, 

 although displaying great variation in position can in most cases 

 be reduced to the following classification: (1) right medial hepatic 

 ramus, (2) left medial hepatic ranius, (3) anterior right hepatic 

 ramus, (4) posterior right dorsal hepatic ramus, (5) anterior left 

 hepatic ramus, (6) posterior left dorsal hepatic ramus. 



The right medial hepatic ramus varies considerably in the place 

 of origin, commonly it is attached to the right duct near its proxi- 

 mal end. The left medial hepatic ramus commonly takes origin 

 from the proximal part of the left hepatic duct but may in some 

 cases be attached to the ductus choledochus or even to the base 

 of the right hepatic duct. The anterior right and the anterior 

 left rami generally arise from the summit of the anterior arch 

 formed by each of the main hepatic ducts, but the left ramus may 

 attach either to the ductus choledochus, or as I have observed in 

 one embryo, to the base of the main right hepatic duct. The 

 posterior dorsal hepatic rami arise from the hepatic ducts either 

 at the lateral extremity of the anterior arch or in the anterior 

 part of their posterior course. They seem to be fairly constant 

 in position. Minor variants from the above scheme are common 

 and simple rami differ much in size or may be replaced by two or 

 more smaller ones. The terminology used here is based upon 

 the development of these structures as will now be described. 



