262 EMBRYOLOGICAL METHODS. 



cut out with a knife or fretsaw, cutting through the cardboard ; and 

 the pieces of fretwork thus obtained are pasted together. 



Many useful modifications of this method have been devised. 

 Cardboard is rather hard to cut, and not conveniently got of the 

 required thickness. Professor Arthur Thompson, of Oxford, uses 

 numbers of sheets of blotting paper to the required thickness, 

 soaked in beeswax ; this makes a very tough substance, and the 

 models, when made, can be handled without chance of injury ; 

 other workers use beeswax plates alone, drawing the outline with 

 some sharp instrument and cutting out with a hot knife. 



Mr. Pittock, of the Zoological Laboratory, University College, 

 London, uses a modification of K. Peter's method (vide infra). 

 Rather thin paper is used for drawing the outline of the object. In this 

 laboratory (Professor J. P. Hill), special rolls of paper are used, so 

 that the diagram of each of hundreds of sections may be safely 

 rolled up in or,der till wanted. A large flat stone is used for the 

 manufacture of the wax plates, with two brass gauges of the required 

 thickness placed at a distance which will accommodate in between 

 them the square of paper with the drawing. Instead of treating the 

 paper with turpentine, according to Mr. Pittock's method the 

 drawing is rapidly floated over the surface of a dish of water, drawing 

 side down, then laid upon the stone, between the metal gauge and 

 the superfluous moisture smoothed off with a sheet of blotting 

 paper. The melted wax is poured on to the paper, and a heated 

 metal roller passing over the metal gauge leaves just the required 

 amount of wax on the paper. The latter easily peels off the surface 

 of the stone. 



For more elaborate processes of plastic reconstruction (very compli- 

 cated and seldom necessary) see BORN, " Die Plattenmodellirmethode," 

 in Arch. mik. Anal., 1883, p. 591, and Zeit. wiss. Mik., v, 1888, p. 433 ; 

 STRASSER, ibid., iii, 1886, p. 179, and iv, pp. 168 and 330 ; KASTSCHENKO, 

 ibid., iv, 1887, pp. 235-6 and 353, and v, 1888, p. 173 ; SCHAPER, ibid., 

 xiii, 1897, p. 446 ; ALEXANDER, ibid., p. 334, and xv, 1899, p. 446 ; 

 PETER, ibid., xxii, 1906, p. 530 ; BORN and PETER, ibid., xv, 1, p. 31 ; 

 and Verh. Anat. Ges., xiii, 1899, p. 134 ; JOHNSTON, Anat. Anz., xvi, 

 1899, p. 261 ; FOL, Lehrb., p. 35 or previous editions ; BROMAN, Anat. 

 Hefte, xi, 1899, p. 557 : PETER. " Die Methoden d. Eekonstruction " 

 (Fischer, Jena, 1906) ; SCHONEMANN, Anat. Hefte, xviii, 1901, p. 117; 

 GAGE, Anat. Record, i, 1907, p. 167 ; NETJMAYER, Festschr. f. Kupffer, 

 1899, p. 459 ; MARK, Proc. Amer. Acad. Sci., xiii, 1907, p. 629 (electric 

 wax-cutter for cutting out plates). 



HILL (Butt. Johns Hopkins Hasp., xvii, 1906, p. 114) finds that 

 embryos of mammalia taken from 95 per cent, alcohol and put into 

 caustic potash of 1 per cent, become so transparent that they can be 

 studied without cutting and reconstructing. 



