96 PARAFFIN METHOD 



For methods for ascertaining melting-points see Kissling, 

 Chem. Centralb., ii, 1901, p. 507. 



Ceresin Method of Higgs, Waddington and Kriebel. This 

 method has been worked out independently by Waddington 

 and Kriebel (Nature, October 26th, 1935) and 'Espinasse 

 (communicated), the former for use in sectioning hard embryonic 

 material, the latter for developing feathers. That the addition of 

 ceresin alters the physical structure of paraffin wax practically to 

 micro-crystallinity was first pointed out by P. G. Higgs in a paper 

 read before the Institution of Petroleum Technologists in December 

 11th, 1934, and reported in Nature, January 19th, 1935. 'Espinasse 

 obtained some ceresin and found it remarkably good for his work 

 on feathers, while Waddington and Kriebel have used it for 

 sectioning yolky eggs and embryos, and reported very favourably 

 on it. Waddington uses various mixtures of ceresin and wax 

 even as low as 0-5 per cent., with great benefit. Ceresin itself, 

 or mixtures of ceresin and wax, with a high proportion of the 

 former must be melted in a beaker in a vessel placed in hot water, 

 as the temperature necessary is too high to be got with a normal 

 oven. 'Espinasse used the following mixture : paraffin wax 

 (M.P., 52° C), Woolworth candles (suggested by Dr. Henderson 

 of Hull) and ceresin (M.P. circa 72° C), 1 part each. This makes 

 a very hard mixture and should be filtered. The candles supplied 

 by Messrs. Woolworth, Mr. 'Espinasse informs us, have a low 

 melting-point, but add greatly to the smoothness of the mixture. 



Methyl Benzoate Celloidin Ceresin Method of 'Espinasse (com- 

 municated). The methyl benzoate method of Peterfi has been 

 combined with the ceresin method for cutting very hard objects. 

 It will give thin sections of small Crustacea developing feathers, 

 etc., and in one case gave excellent sections of the human pituitary 

 and infundibular region. Dissolve 10 grm. of perfectly dry 

 celloidin in 1 litre of methyl benzoate. Use this for clearing 

 from ethyl alcohol. Objects may be left weeks without hurt. 

 Transfer to pure benzol for a few minutes in the case of small 

 objects, or some hours for larger specimens. Bring into wax, 

 using the mixture mentioned in the previous paragraph. Then 

 prepare a very hard mixture (higher proportion of ceresin) heated 

 in a beaker ; this is poured into a mould, and when beginning to 

 cool, it receives the object. 



178. Overheated Paraffin. Spee (Zeit. wiss. Mik., ii, 1885, p. 8) takes 

 paraffin of about 50° C. melting-point and heats it in a porcelain capsule 

 by means of a lamp until it has become brownish-yellow, and after 

 cooling sliows an unctuous or soapy surface on being cut. This mass 

 may be obtained ready prepared from Grubler. The object of this 

 preparation is to make the mass stickier, in view of cutting ribbons. 



Van Walsem (Verh. Akad. Wetensch. Amsterdam, 1899, p. 132) still 

 recommends the addition of 5 per cent, of yellow wax to paraffin of 52° 

 to 57° melting-point (for large sections of central nervous system). 



