RECONSTRUCTION OF EMBRYOS FROM SECTIONS. 259 



writing the chapter on embryological methods for the French 

 edition of this work, advised staining in the mass with borax- 

 carmine or alum-carmine (Henneguy's acetic-acid formula, 

 151) ; or, as an alternative, the staining of sections by 

 Flemming's method. The improvements that have in recent 

 times been worked out in this method give still greater weight 

 to the latter recommendation. 



554. Reconstruction of Embryos from Sections. The study of 

 a series of sections of any highly differentiated organism of 

 unknown structure is so complicated that it is often necessary 

 to have recourse to elaborate methods of geometrical or of 

 plastic reconstruction in order to obtain an idea or a model 

 of the whole. These methods have now been brought to so 

 high a degree of complexity that a volume rather than a 

 paragraph would be necessary to describe them. See BORN, Die 

 Plattenmodellirmethode, in Arch. f. mik. Anat., 1883, p. 591, 

 and Zeit. f. wiss. Mik., v, 4, 1888, p. 433; STRASSER, in Zeit. 

 f. wiss. Mik., iii, 2, 1886, p. 179, and iv, 2 and 3, pp. 168 and 

 330; KASTSCHENKO, in Zeit. f. wiss. Mik., iv, 2 and 3, 1887, 

 pp. 235-6 and 353, and v, 2, 1888, p. 173 (abstracts of all 

 these papers may be found in Journ. Roy. Mic. Soc. of the 

 years quoted). 



A simple, but in many cases quite efficient plan, has been described by 

 FOL (Lehrb., ip. 35), as follows. Before cutting your sections, you make 

 an outline drawing of your object, under the magnification that you intend 

 to employ for the reconstructed drawing, and in a plane perpendicular to 

 that of the intended sections. For instance, if you intend to make trans- 

 verse sections of an embryo, begin by making a profile drawing of it, that 

 is, a drawing of the outline of an ideal sagittal section of it. Then make 

 your series of sections, and make drawings of them all under the same 

 magnification as the sagittal drawing. Then trace over your sagittal draw- 

 ing a series of equidistant parallel lines in positions corresponding to the 

 sections that have been made. If your sections are one hundredth of a 

 millimetre thick, and your drawing be magnified one hundred times, the 

 lines should be one millimetre apart (if you intend to reconstruct the whole 

 of your sections, but the operation may frequently be abridged by only 

 reconstructing say every fifth or every tenth section). 



You have now to fill in your outline drawing with details borrowed from 

 the drawings of the sections. You may help yourself greatly in the follow- 

 ing way. A plate of glass, of a size suitable to the intended drawings, is 

 covered with a layer of gelatin, and dried. On this is ruled a series of 

 parallel lines, very close together, and ruled with differently coloured inks, 

 the colours recurring in regular order. The plate is then cut into two un- 

 equal parts by a diamond, on a line perpendicular to the coloured lines. 



