CHAPTER IX. 105 



should be added, so as to bring the mixture up gradually to nearly 

 pure cedar oil. As soon as the object is cleared throughout, the 

 mass may be exposed to the air, and the rest of the chloroform will 

 evaporate gradually. The block may now either be mounted on 

 the holder of the microtome, 165, and cut at once, or may be 

 preserved indefinitely without change in a stoppered bottle. Cut 

 dry, the cut surface will not dry injuriously under several hours. 

 The cutting quality of the mass is often improved by allowing it to 

 evaporate in the air for some hours. 



The hardening may be done at once in the chloroform and cedar 

 oil mixture, instead of the chloroform vapour, but I find the latter 

 preferable. And clearing may be done in pure cedar oil instead of 

 the mixture, but then it will be very slow, whereas in the mixture 

 it is extremely rapid. 



STEPANOW (Zeit. wiss. Mik., xvii, 1900, p. 185) soaks and imbeds in a 

 solution of celloidin in a mixture of equal parts of ether and clove oil, 

 hardens in alcohol or vapour of chloroform, or in benzol, and cuts either 

 wet or dry. 



See also TSCHERNISCHEFF, ibid., p. 449. 



JORDAN, ibid., p. 193, imbeds in a mixture of 5 parts of 8 per cent, 

 celloidin solution with 1 of oil of cedar, hardens first in vapour of 

 chloroform and then in a mixture of 5 parts of chloroform with 1 of oil 

 of cedar, and cuts wet or dry. 



171. Double Imbedding in Collodion and Paraffin. This is some- 

 times employed for objects of which it is desired to have very thin 

 sections, and which are too brittle to give good sections by the plain 

 paraffin process. 



KULTSCHITZKY'S Method (Zeit. wiss. Mik., iv, 1887, p. 48). 

 After the collodion bath, the object is soaked in oil of origanum 

 (Oleum Origani vulg.). It is then brought into a mixture of origanum 

 oil and paraffin heated to not more than 40 C., and lastly into a bath 

 of pure paraffin. 



The mass maybe preserved in the dry state, and maybe cut dry. 



RYDER (Queen's Micr. Bull, 1887, p. 43 ; Journ. Roy. Micr. Soc., 

 1888, p. 512) modified the process by substituting chloroform for the 

 origanum oil. 



IDE (La Cellule, vii, 1891, p. 347, and viii, 1, 1892, p. 114) imbeds in 

 collodion in a tube by GILSON'S process ( 169) ; the collodion is boiled 

 for forty minutes, then brought for fifteen minutes (this is for smal 

 objects) into chloroform heated to 30 C. containing part of paraffin 

 dissolved in it, then for ten minutes into pure melted paraffin. 



FIELD and MARTIN (Bull. Soc. Zool. de France, 1894, p. 48) make 

 solution of dried celloidin in a mixture of equal parts of absolute alc< 

 and toluene, of about the consistency of clove oil. This solution 11 



