1883.] Microscopy. III 
structure may be obtained? One might be tempted to lock it up 
as a cabinet rarity, if he did not know how to make a single series 
of sections tell the whole story. If the preliminary steps have 
been correctly taken, it is possible to construct from serial trans- 
verse sections, a median sagittal (longitudinal and vertical) or 
frontal section, or a section in any desired plane. From the same 
series may be constructed also surface views of internal organs, 
which are inaccessible to, or unmanageable by, any of the ordi- 
nary methods of dissection. 
It frequently happens that sections can be obtained by construc- 
tion that could not be obtained by any direct .means, For 
example, we may desire a frontal section of a vertebrate embryo 
that will show all the parts that lie in the same level with the 
chorda, or a sagittal section that will represent a median plane. 
It is evident that no such sections can be directly obtained, owing 
to the axial curvature of the embryo; but they can easily be con- 
structed from transverse sections. It is here that we see some of 
the great advantages to be derived from the use of the microtome. 
It not only overcomes the opacity of objects, but it also enables us 
to represent curved and twisted surfaces in plane surfaces. The 
ability to construct sections at right angles to the actual planes of 
section is the key to the next and final step—‘ the plastic synthe- 
sis” of the sectioned object. 
METHOD oF RECONSTRUCTION.—Professor His was the first to 
' His. “ Untersuchungen ü. d. erste Anlage des Wirbelthierleibes,” p. 182, 1868 
t ‘Neu Untersuchungen ü. d. Bildung des Hühnerembryo, in Arch. f. Anat. u 
hysiol., anat. Abth.,”’ p. 122, 1877. 
s Seessel “Arch. f. Anat. u. Physiol., anat., Abth.,” p. 449, 1877. 
, Foree. Morph. Jahrb. Vol. 1, p. 108, 1875. 
_ Krieger. Zeits: hrift f. wiss. Zool. Vol. XXXIII, p. 531, 1880, and Zool. Anzeiger» 
P. 369, 1878. er 
