90 The Microscopic Structure — | Wournai, Aue 1, 0. 
low power, it is put upon the glass plate of the “microscopic dis- 
sector,” and kept in place by the small lever. Before commencing 
the dissection with this instrument under the compound microscope, 
it is advisable to re-examine the preparation under the simple mag- 
nifying lens on the dissecting stage, taking care that it 1s nicely 
spread upon the glass, so that the ultimate branches of the hepatic 
duct, or of the blood-vessels, do not overlap each other. The micro- 
scopic dissector, with the preparation upon its glass plate, is now 
placed upon the stage of the compound microscope, and after a 
small branch of the hepatic duct—with some of the parenchyma 
still adhering and rendering it favourable for research-—has been 
found under an objective of 43-inch focal length, the dissection 
with the curved needles of the instrument may be commenced. 
After the needles have been made to take hold of the preparation 
at the proper places, an objective of a higher power may be em- 
ployed. The curved points of the needles, of course, must be short 
enough not to interfere with the approach of the objective in 
bringing the object into its focus. 
If a dissection, as just described, is made successfully, the finest 
branches of the hepatic duct will be seen to commence in a capillary 
network. A fine duct may be seen in company of its corresponding 
portal vein and hepatic artery, and, likewise, their finest branches, 
each originating in its respective vessel, and terminating in the 
capillaries. The ducts can always be distinguished from blood- 
vessels by their characteristic epithelium. By moving the needle 
which holds the finer extremity of the duct, it will be observed that 
the meshes of the “biliary tubules,” arising from it, move also, 
while the capillaries, arising from the blood-vessels, remain sta- 
tionary; this manceuvre, if well executed, removes every doubt 
which might still exist in regard to the origin of the finest hepatic 
ducts. A great deal of patience and manipulative skill, however, 
are required to make such delicate dissections, and the investigator 
must not become discouraged when he finds that his labours are 
not always crowned with success. All he can do when failing, is 
to try it again. 
When the biliary tubules have once been satisfactorily demon- 
strated by the skill and perseverance of the investigator, he will be 
able to recognize them—without the aid of the microscopic dissector 
—in preparations carefully made on the dissecting stage. 
The commencement of the finest branches of the lymphatics in 
the network of “biliary tubules” can only be demonstrated by in- 
jection. In removing cautiously the parenchyma, in which the 
“biliary tubules” are well injected with Prussian blue, from the 
“capsule of the portal vessels,” and then dissecting, under water, 
a thin layer from the outside of the latter, the lymphatics can often 
be seen arising from very fine vessels, derived from the “ biliary 
