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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

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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

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