134 CHAPTER IX. 



one or two parts of cedar oil. From time to time more 

 cedar oil 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 be mounted on the holder of the micro- 

 tome with a drop of thick collodion, 159, and may either 

 be 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- wood mixture, instead of the chloroform vapour, but I 

 find the latter process preferable, as giving a better harden- 

 ing. 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. 



166. Double Imbedding in Collodion and Paraffin. This com- 

 plicated process is sometimes, though rarely, 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. I do not think that in any form, 

 hitherto published it can be considered to be a success. 



KULTSCHITZKY'S Method (Zeit.f. wiss. Mik., iv, 1, 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 may be preserved in the dry state, and may be cut dry. 



RYDEE (Queen's Micr. Bull, 1887, p. 43 ; Journ. Roy. Mic. 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) employed 

 with success the following method : The object is imbedded in collodion in 

 a tube by GILSON'S process (supra, 164) ; the collodion is boiled for forty 

 minutes, then brought for fifteen minutes (this is for small objects) into 

 chloroform heated to 30 C. containing one fourth part of paraffin dissolved 

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



FIELD and MAETIN (Bull Soc. Zool.de France, 1894, p. 48), finding that 

 it is difficult to get hardened celloidin masses adequately impregnated with 

 the paraffin, have worked out the following process of simultaneous 

 imbedding. A solution of dried celloidin in a mixture of equal parts of 

 absolute alcohol and toluene, of about the consistency of clove oil, is made. 

 This solution is saturated with paraffin, added in shavings at a temperature 

 not exceeding 20 to 23 C. The tissues are prepared by soaking in some of 

 the mixture of alcohol and toluene, and are then penetrated with the 



