10 
DR. C. H. JONES ON THE STRUCTURE, DEVELOPMENT 
ducts were clearly seen in this instance to pursue a long course with veiy little rami- 
fication ; one branch I traced for-^th of an inch without observing any branch given 
olF from it, or scarce any diminution in its diameter. 
Develo'pment in Reptiles. 
In Reichert’s description of the development of the embryo of the Frog (von 
Muller’s Physiology), it is stated that the anterior part of the mass of yolk contained 
in the cavity of the abdomen isolates itself from the rest of that substance, and 
becomes an independent body ; which constitutes the rudimentary mass from which 
the liver and pancreas are subsequently formed. This I think I have also observed, 
or at least that as soon as the yolk mass begins to take the form of an intestinal tube 
a portion of it remains separate, constituting two masses, a larger and a smaller, 
which lie one on each side of the nascent intestine. When development had advanced 
a little further, and the intestine was manifestly formed, I found the parenchyma ot 
the liver lying close in contact with it, and also a small vesicle adhering to the mass 
of the liver, which was certainly the rudiment of the gall-bladder. The future liver 
consisted of multitudes of large vesicular nuclei lying imbedded in oily matter, and 
the whole mass was surrounded by an investing homogeneous tunic. The gall- 
bladder in its earliest appearance was simply a spherical mass of similar constitution 
to that of the liver ; subsequently it presented a distinct membranous wall lined inside 
by a close layer of large vesicular nuclei, the interspaces between which were occupied 
by oil-drops. It assumed very soon more or less of a pyriform shape, and became 
connected with a narrow tract stretching down to the intestine which cleaily lepie- 
sented the cystic duct ; this tract consisted of similar formative substance to that 
composing the liver and the g'al I- bladder ; from it in a more advanced stage oflTsets 
were developed having the same constitution, and extending into the substance ot 
the liver ; these were beyond doubt rudimentary hepatic ducts. In one instance, uheie 
the gall-bladder existed, but was certainly not connected by a duct with the intes- 
tine, I saw lying by its side a short tract consisting of similar material, which was 
partially divided at its peripheral extremity ; this seemed to be an early rudiment of 
an hepatic duct. The rudimentary ducts appeared to me to be solid tracts ; I could 
not at this period detect a cavity in the interior ; subsequently they beeome invested 
with a homogeneous tunic on their exterior, and the vesicular nuclei arrange them- 
selves in the form of an epithelial lining, the interspaces between the nuclei being 
occupied with oily matter. Both in the gall-bladder and in the ducts this oily matter 
gradually disappears; the epithelium of the former comes to present the ordinary 
form of a pavement, while that of the common duct developes cilia which are seen in 
vigorous action, exciting a current downward from the liver to the intestine. I do 
not know exactly how long this ciliary action continues to be present in the hepatic 
duct ; I have observed it for about a month from the date of its first appearance. As 
development advances the oily matter in the parenchyma of the liver diminishes, and 
