ARRANGEMENT OF THE BILIARY DUCTS. 
379 
Method of injecting the Ducts of the Liver and the Cell-containing Networh. 
Although I felt certain of the correctness of my observations upon various imin- 
jected specimens examined two years since (in 1853), it appeared to me that it must 
be possible to inject both the minute ducts and the hepatic cell-containing network, 
if they were really continuous, and for a long time past I have been endeavouring to 
effect this object. It w'ould be useless here to describe all the different plans I have 
resorted to, and I shall therefore only refer to the method which succeeded. After 
failing many times to drive the injection into the smallest ducts, it occurred to me 
to try to empty the ducts of their bile before injecting them. This object was at last 
readily obtained by forcing water into the portal vein, and causing the vessels to 
become distended. In consequence of this distension, the ducts were compressed, 
and the bile was forced from the small into the larger branches. After continuing 
the injection of the water for a short time, bile trickled from the duct and the gall- 
bladder became filled — soon bile ceased to escape, and almost pure water flowed. 
After the liver had been thoroughly drained, by being placed in soft cloths for some 
hours, the duct was injected with Prussian blue*. The injection passes readily with 
slight force, and can be seen entering the lobules upon the external surface of the 
liver. It does not appear gradually round the circumference of the lobule as when 
the portal vein is injected, but it forms small roundish points, almost like extravasa- 
tions, here and there at the outer part of the lobule, and it spreads from thence 
towards the centre. 
After the duct has been injected in this manner, it becomes necessary to distend 
the capillary vessels with injection, otherwise a thin section has a confused appear- 
ance. For this purpose plain clear size is the best. The portal vein is injected with 
it, and the injection continued until the whole organ is fully distended. The vessels 
* Before resorting to Prussian blue I had tried numerous different substances. Opake injections always 
caused the preparation to look confused under high powers, and it was impossible completely to remove the 
adhering particles of injection from the section by washing. In consequence the specimen never looked clear. 
Transparent injections seemed likely to afford more favourable results, and several were tried. Most of them 
passed through the walls of the ducts, colouring all the adjacent tissues, and afforded no better success than 
opake injections. Carefully prepared Prussian blue combines the advantages of an opake injection with 
those of a coloured solution. The particles vidll not pass through basement membrane, and at the same time 
they are so minute, that when suspended in fluid, the appearance of a solution is produced. Injections of 
Prussian blue may be examined by reflected or by transmitted light. 
The Prussian blue is prepared in the usual manner, by adding a solution of ferrocyanide of potassium to a 
dilute solution of perchloride of iron. The mixture should have the appearance of a dark blue solution, and 
should contain no flocculi. It should not form a deposit until it has stood for some time. About a third of its 
bulk of spirit should be slowly added and the mixture well stirred. The advantage of the spirit is, that it 
hardens the delicate walls of the finer ducts as it comes in contact with them, and thus tends to prevent their 
rupture. The mixture must be strained through two or three layers of fine muslin before use. The Prussian 
blue may be injected by means of a small half-ounce syringe, or by the pressure of a column of fluid about 
four feet in height placed in a long tube. 
