CHAPTER VIII. si 



In using the needle it is important to melt as little paraffin as possible 

 at one time, in order that that which is melted may cool again as 

 rapidly as possible. 



KERR (Quart. Journ. Micr. Sc., xlv, 1901, p. 4) employs an 

 electrically heated needle. 



The method of PATTEN (Zeit. wiss. Mik., xi, 1894, p. 13) is useful 

 when one desires to orient large numbers of small objects. You get 

 some writing paper of the sort that is made with two sets of raised 

 parallel lines running at right angles to each other (''linen cloth 

 paper "). Small strips are cut from this, and at suitable intervals along 

 them small drops of a mixture of collodion and clove oil, of about the 

 consistency of thick honey, are arranged close together along one of the 

 ribs that run lengthwise. The objects to be imbedded are cleared in 

 clove oil or oil of bergamot. They 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. 



KNOWEN (Journ. 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 WOOD WORTH, Butt. Mus. Comp. Zool., xxxviii, vol. xxv, 1893, p. 45. 

 A similar process has also been described by FIELD and MARTIN in 



Zeit. wiss. 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. Nik., xv, 1899, p. 312, and xvii, 1901, p. 443) 



takes, instead of the ribbed 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, Verh. Anat. Ges., 



xiii Vers., 1899, p. 134. 



ENTZ (Arch. Protistenk., 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 be detached. 



DENNE (Journ. Appl. Mic., iii, 1902, p. 888) imbeds on disks of paper 



held at the bottom of glass tubes containing the paraffin by bent wires, 

 M. 6 



