IMI!KI>IHN<; MKTIIODS. 87 



Tliey are taken one by one on the point of a knife, and after 

 the excess of oil has been drawn off, are transferred each to a drop of 

 the collodion mixture, in which they will stay in any required position. 

 When half a dozen or more objects have been oriented in reference to 

 the cross lines (which are to be parallel to the section planes) the whole 

 thing is placed in turpentine. This washes out the clove oil and fixes 

 the objects very firmly to the paper. The paper with the attached 

 objects is now passed through the bath of paraffin and imbedded in the 

 usual way. After cooling on water the block is trimmed and the paper 

 peeled off, leaving the objects in the paraffin close to the under-surface 

 of the block. This surface is now seen to be marked by the orienting 

 lines of the ribbed paper, and also by any record numbers which may 

 before imbedding have been written with a soft pencil on the paper. 



' KNOVVEN (Jouni. Morph., xvi, 1900, p. 507) takes smooth paper and 

 engraves parallel lines on it with a needle, and takes xylol instead of 

 turpentine. 



A somewhat more complicated form of this process has been 

 described by WOODWORTH, Bull. Mus. Comp. Z-tol., xxxviii, vol. xxv, 

 1893, p. 45. 



A similar process has also been descril>ed by FIELD and MARTIN in 

 Zeit. iviss. Mik., xi, 1894, p. 11, small strips of gelatin being used instead 

 of paper. 



MAYER also (Grundzuge, LEE and MAYER, 1910, p. 89) takes strips of 

 photographic gelatin, and lets the collodion set in benzol. 



HOFFMANN (Zeit. wiss. Mik., xv, 1899, p. 312, and xvii, 1901, p. 443) 

 t;ik>'.s. instead of the ribted paper, glass slips ruled with a diamond, and 

 completely imbeds the objects in large drops of clove oil collodion 

 (equal parts), allowed to stand for twenty-four hours in an open vessel. 

 The drops are caused to set in xylol. See also SAMTER, ibid., xiii, 1897, 

 p. 441 ; JORDAN, ibid., xvi, 1899, p. 33 ; and PETER, Verli. Anat. Ges., 

 xiii Vers., 1899, p. 134. 



ENTZ (Arch. Frotistenh:, xv, 1909, p. 98) orients in clove oil collodion 

 on a cover-glass coated with paraffin, and puts the whole into chloroform 

 in which the mixture sets into a sheet which can }ye detached. 



DENNE (Journ. AppL. Mic., iii, 1902, p. 888) iml>eds on disks of paper 

 held at the lx>ttoni of glass tubes containing the paraffin by l>ent wires, 

 by means of which a cylinder of paraffin containing the object may Jje 

 lifted out as soon as cool. 



WILSON (Zeit. wiss. Mik., xvii, 1900, p. 169) makes orientation lines by 

 imtedding alongside the objects strands of osmium-blackened nerve- 

 fibres. See also a further development by Wilson, ibid., xxvii, 1910, 

 pp. 228 and 231. 



143. Cooling the Mass. Whatever method of imbedding 

 and orientation in the molten paraffin has been employed, 

 the important point now to be attended to is that the paraffin 

 lv coolvd rapidly. The object of this is to prevent crystalli- 



