The microscope and its revelations . .^-3^^ g^^^ *^^ compactness ifih/:; ^!)<^^0 Af/A^ the solid portion be strengthened. Generallyspeaking, the differentlayers of this network,which are connected to-gether by pillars thatpass from one to theother in a direction per-pendicular to their plane, are so arranged that the perfo-rations in one shall correspond to the intermediate solidstructure in the next; and their transparency is such, that when we are examiningFig, 235. a section thiii enough to contain only two or threesuch layers, it is easy, byproperly focussing theMicroscope, to bringeith
The microscope and its revelations . .^-3^^ g^^^ *^^ compactness ifih/:; ^!)<^^0 Af/A^ the solid portion be strengthened. Generallyspeaking, the differentlayers of this network,which are connected to-gether by pillars thatpass from one to theother in a direction per-pendicular to their plane, are so arranged that the perfo-rations in one shall correspond to the intermediate solidstructure in the next; and their transparency is such, that when we are examiningFig, 235. a section thiii enough to contain only two or threesuch layers, it is easy, byproperly focussing theMicroscope, to bringeither one of them intodistinct view. From thisvery simple but verybeautiful arrangement, itcomes to pass that theplates of which the entire test is made-up, possessa very considerable de-gree of strength, not-withstanding that theirporousness is such, thatif a portion of a fractured edge, or any other part from whichthe investing membrane has been removed, be laid upon fluidof almost any description, this will be rapidly sucked-up into. Transverse Section of medullary por-tion of Spine of Acrocladia, showing itsmore open network. CALCAREOUS SKELETON OF ECHINIDA. 555 its substance. A very beautiful example of the same kind of cal-careous skeleton, having a more regular conformation, is fur-nished by the disk or rosette which is contained in the tip of everyone of the tubular suckers put-forth by the living Echinus fromthe ambulacral pores of its shell. If the entire disk be cut-ofp,and be mounted when dry in Canada balsam, the calcareousrosette may be seen well; but its beautiful struc-ture is better made-out, when the animal membrane thatencloses it has been got-rid-of by boiling in caustic potass;and the appearance of one of the five segments of which it iscomposed, when thus prepared, is shown in Eig. 236. Fig. 236.
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Keywords: ., bookcentury1800, booksubjectmicroscopes, booksubjectmicroscopy
