106 GUIDE TO THE STUDY 



tion in pure glyercine. Care must be taken to insure that they 

 are not exposed as the mixture evaporates. 



The above-described method is not suitable for such forms 

 as Trichosomum, Trichuris, and the like, since they become 

 tightly coiled and shrink. Magath found that this could be 

 prevented in great measure by placing the points of a pair of 

 forceps together and working the specimens to and fro in the hot 

 fluid as soon as placed in it. In applying this method- the fluid 

 should first be heated and then the worms transferred to it. 



Nematodes which have been gradually brought into pure 

 glycerine, as above, may be permanently mounted in glycerine 

 jelly and the cover glass sealed with Noyer's cement or with 

 very thick Canada balsam. 



A simple and very satisfactory method of preservation and 

 mounting recommended by Langeron is that of killing in 5 per 

 cent formalin and transferring after several hours into lacto- 

 phenol mixture. They may be mounted directly in this mixture 

 and the cover glass sealed as above. 



For preservation of histological detail Magath recommends 

 killing in 50 per cent alcohol heated to 60 to 75°C. and trans- 

 ferring at once to a mixture of equal parts of alcohol, water, 

 and acetic acid to which has been added 0.05 to 0.1 per cent osmic 

 acid. In this the material is left for from 1 to 10 hours, depending 

 on size. 



The same author describes in detail a technique for infiltrating 

 and mounting in Canada balsam, though this medium is thor- 

 oughly unsatisfactory for nematodes when the ordinary technique 

 is attempted. 



It should be noted that nematodes preserved in formalin 

 or in alcohol can be cleared for temporary study by transferring 

 to a mixture of 4 parts of melted carbolic acid crystals and 1 

 part absolute alcohol. 



References 



Hall, M. C, and E. B. Cram, 1925. Some laboratory methods for parasi- 

 tological investigations. Jour. Agr. Research, 30 (8) : 773-776. 



Magath, T. B., 1916. Nematode technique. Trans. Am. Micro. Soc, 

 35 (4) : 245-256. 



SOIL NEMATODES 



Various methods for the isolation of not only soil inhabit- 

 ing parasitic stages but also free-living nematodes from the 



