MINUTE ANATOMY OF THE LIVER.

CHAPTER I.

OF THE METHOD OF INVESTIGATION.-HARDENING THE LIVER. —SYRUP.—ALCOHOL AND SODA; THEIR USE IN RENDERING ALBUMINOUS TISSUES TRANSPARENT.-METHOD OF INJECTING THE DUCTS OF THE LIVER AND THE HEPATIC CELLCONTAINING NETWORK. OPAQUE INJECTIONS. -TRANSPARENT INJECTIONS.-PRUSSIAN BLUE.-DIRECTIONS FOR INJECTING THE DUCTS OF A LIVER FOR EXAMINATION WITH HIGH POWERS OF THE MICROSCOPE.-PREPARING THE INJECTING FLUID.—OF INJECTING THE VEINS WITH PLAIN SIZE. PREPARATION OF SPECIMENS PREVIOUS TO EXAMINATION IN THE MICROSCOPE.

In the following inquiry I have employed several methods of investigation which differ in many important particulars, as far as I am able to ascertain, from those which have been followed by other observers. As I believe that my success is to be attributed solely to the methods employed in the inquiry, it seems to me important that they should be described in detail before the results of the investigations are referred to.

METHOD OF PREPARING SPECIMENS TO SHOW THE CONTINUITY OF THE DUCTS WITH THE CELL-CONTAINING NETWORK.

I have not found it possible to demonstrate very satisfactorily the arrangement of the ducts and cell-containing network of the liver, without previous preparation, although I have succeeded in making it out, in some instances, in perfectly fresh specimens examined in glycerine. The difficulty of deciding the point in recent preparations need not excite surprise if the extreme softness of the liver and the difficulty of cutting thin sections

B

are taken into consideration. Some observers altogether object to observations made upon specimens which have undergone previous preparation, forgetting that water often exerts a more powerful influence in altering the natural appearance of the structure than many of the fluids to the use of which they object. The alteration in the appearance of a structure effected by the refractive power of the medium in which it is immersed is often very great, and must be taken into consideration in examining different textures. Thus, the same body presents a very different appearance when examined in air, water, syrup, oil, or Canada balsam, although neither of these media may have any chemical action on the substance immersed in them. Again, a delicate tubular membrane will entirely collapse in a limpid fluid like water, while in syrup or glycerine it would retain its original appearance. In the first case all tubular character would be lost, while in the second, it would remain distinct. In the present investigation it is important to consider these points.

Hardening the Liver.-In order to show the minute ducts in an uninjected specimen, it is necessary to harden the liver. This hardening may be effected by placing small pieces in syrup for some weeks, or in dilute alcohol to which a few drops of solution of soda have been added. Of the value of this last mixture I cannot speak too highly. No mode of preparation has afforded me such satisfactory specimens, not only of the liver, but of many other tissues, as the one referred to. The advantage of this solution seems to depend upon the opposite action of the two fluids. The alcohol precipitates albuminous compounds, and renders them hard and opaque. The soda, on the other hand, softens and dissolves them, rendering them transparent. In conjunction, these operate in rendering the tissue quite hard and transparent at the same time. I am still prosecuting experiments with this fluid. Large preparations have been preserved in the alkaline fluid with advantage. I have a beautiful preparation of the fœtus, about the fourteenth week, showing the ossification of all the bones. The condition of those of the extremities is particularly interesting. All the textures are perfectly transparent, while the calcareous matter remains opaque.

In this manner the portion of liver is made perfectly hard, but

at the same time transparent. a very sharp, thin knife, then slightly washed and examined in dilute alcohol or glycerine. In many of the sections thus prepared, the appearances represented in some of the drawings in the present volume were produced. The same success is by no means always met with, and it is necessary to examine numerous specimens treated in different ways. Some of my preparations were obtained from the livers of animals in which the duct had been tied some hours before death; and others were taken from organs into the duct of which injection had been gradually forced until it would contain no more. Small pieces were then hardened, and examined after the lapse of some time.

A thin section is to be made with

But, although, in many instances, I was able to satisfy myself of the truth of the most important points which I have to bring forward with regard to the arrangement of the minute ducts, a vast number of the preparations failed altogether, and I could not demonstrate the arrangement in every liver which I tried, so that I was compelled to resort to new means of preparation. Injection I had tried many times, and had only succeeded so far as consisted in driving the bile into the small ducts. I could not force the injection far enough. The injection usually only reached the surface of the hepatic cell-containing network, and, in many instances, accumulated at this point, in which cases, the appearance of a duct terminating in a blind extremity was produced.

Method of Injecting the Ducts of the Liver, and the Hepatic Cell-containing Network.-Although I felt certain of the correctness of my observations upon uninjected specimens, it appeared to be absolutely necessary to inject both the ducts, and from these, the cell-containing network, before their continuity could be regarded as proved. The presence of the bile in the ducts always prevented the passage of the injection into their most minute ramifications, and no long continued pressure, which I applied by means of a high column of fluid, or with a syringe, was sufficient to force this bile through the thin walls of the duct, and give place to my injection. A most imperfect injection or rupture was the invariable result. After some time it occurred to me to endeavour in the first place to force out the bile by injecting the vascular capillaries with water, and, to my great delight, in the

very first specimen I tried, the gall bladder filled with bile soon after the injection of the portal vein had been commenced, and bile also escaped from the common duct. After a short time, almost pure water ran out from the duct. The water was allowed to escape from the vessels, and then the liver placed in cloths to soak up the water with which it was saturated. The duct, after the lapse of a few hours, was injected. I have examined the water which escaped from the duct upon several occasions. It always contained a large quantity of cylindrical epithelium, and sometimes circular cells from the small ducts were found; but I have never met with specimens of liver-cells, which is easily accounted for, when we consider the small calibre of the smallest ducts. In rare instances these are, no doubt, much larger than natural, in which case the entrance of the hepatic cells would not be prevented. I see, therefore, no reason to doubt the accuracy of Mr. Wharton Jones's observation, although I am unable to confirm it from actual observation.

The injection passed into the ducts very readily and with slight force; and could be seen entering the lobules upon the external surface. It did not appear gradually round the circumference of the lobule, as is the case when the portal vein is injected, but it formed small roundish points, to the unaided eye, almost like little extravasations, here and there at the outside of the lobules; and it then spread for a short distance towards the central part. Upon examining a small piece with the microscope, the small ducts were well seen, and it was evident that they not only went up to the lobules, but that they penetrated into their substance.

Transparent Injections.-Although the injection evidently had not extravasated, the outline of the network was not distinct, and upon examining thin sections with a quarter, only a confused appearance was visible, and I was unable to demonstrate the relation of the cells to the ducts and to the vessels. Before 1 could hope to make out this point, it was clearly necessary not only to inject the ducts, but to inject them in such a manner that they would bear examination with the higher powers (at least a quarter). After trying unsuccessfully many opaque injections, it occurred to me that a transparent injection might succeed better. Camboge, Carmine, Cochineal, Lake, and some other colouring matters were