. The American journal of anatomy. an consists of a ventral median pouchfrom the foregut just anterior to the vitelline duct. The anterior 2 In correlating embryos with stages of Balfours series only the general develop-ment of the embryo has been considered and not the state of development of theorgan under discussion. 250 KICHARD E. SCAMMON part of this pouch is full and rounded and may be termed the parshepatica mediana. From the median pouch spring two largelateral pouches which form together the pars hepatica stages just preceding the appearance of the tubule anlagen thelater
. The American journal of anatomy. an consists of a ventral median pouchfrom the foregut just anterior to the vitelline duct. The anterior 2 In correlating embryos with stages of Balfours series only the general develop-ment of the embryo has been considered and not the state of development of theorgan under discussion. 250 KICHARD E. SCAMMON part of this pouch is full and rounded and may be termed the parshepatica mediana. From the median pouch spring two largelateral pouches which form together the pars hepatica stages just preceding the appearance of the tubule anlagen thelateral pouches are smooth and globose and project outward almostat right angles to the median hepatic pouch. At the time whenthe tubules are formed, however, the lateral pouches are flattenedtransversely and have entered upon a pronounced dorsal with the liver pouch above and in front and with theanterior wall of the yolk stalk behind is a small thick walledsac, the anlage of the gall bladder. The hepatic tubules take. Fig. 1 Lateral view of a semi-diagrammatic reconstruction of the foregutand liver of an Acanthias embryo 9 mm. long. The areas represented in stipplegive rise to hepatic tubules. origin entirely from the pars hepatica mediana and the pars he-patica lateralis. These areas are indicated in stipple in figure tubule anlagen arise in two forms: as slight longitudinalridges upon the lower part of the outer surface of the lateralpouches and as very small irregularities of the dorsal marginsof the same structures. When first observed the longitudinalridges are two to four in number on either side. They extendalmost the entire length of the lateral pouches and are distinctlyseparated by shallow lateral furrows. Sometimes these ridgesmay be subdivided longitudinally at their ends. Figure 17 is aview from the left side and below of the liver of an embryo HISTOGENESIS OF THE LIVER 251 mm. in length ( 14).^ This specimen bears two ridges on theleft
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectanatomy, bookyear1901
