472 THE ANIMAL PARASITES OF MAN 



(4) Glycerine. Vide under methods of preservation of ova ; to mount 

 permanently, transfer to glycerine jelly ; subsequently to harden the jelly, 

 expose to formalin vapour. 



Of these media, carbolic acid has the greatest refractive index excepting 

 that of balsam. The latter may, in some cases, render structures too 

 transparent, and it may be advisable to use only glycerine or glycerine jelly. 



PRESERVATION OF OVA IN FJECES, URINE, BILE, ETC. 



Heat some 70 per cent, alcohol in a basin to about 60 to 70 C. (until 

 bubbles begin to appear). Add the faeces, etc., in the proportion of one 

 part to about nine of fixative ; keep stirring. Allow the sediment to settle. 

 Transfer to a bottle with some fresh 70 per cent, alcohol. 



Transference to Glycerine. Prepare 5 per cent., 10 per cent., 20 per cent, 

 solutions of glycerine in 70 per cent, alcohol. Pour off the alcohol in the 

 bottle of faeces, etc., and replace by 5 per cent, glycerine solution. Allow 

 to stand an hour or so. Then in the same way replace the 5 per cent, by 

 a ID per cent, glycerine, and finally by a 20 per cent, glycerine solution. 

 When in this latter expose freely to the air (protecting from dust), so- 

 as to allow the alcohol and water to evaporate. Add a few drops of 

 glycerine from time to time till eventually the ova are in pure glycerine. 

 (In a very moist climate it may be necessary to use lime or calcium 

 chloride to dry the air.) To mount permanently transfer some of the 

 sediment to glycerine jelly. 



PRESERVATION AND EXAMINATION OF CESTODES. 



Fixation. (i) Saturated aqueous corrosive sublimate. Add to this glacial 

 acetic acid to the extent of i per cent. (Note this fixative will dissolve 

 the "calcareous corpuscles"; 10 grammes of sublimate to 160 c.c. of 

 water will give a saturated solution.) Warm the fixative to 70 to 80 C. 

 (Avoid the use of needles.) Use plenty of fixative. Allow to act for a 

 quarter of an hour or so. (a) Transfer to 70 per cent, alcohol. (It is 

 advisable to remove the sublimate by the use of Lugol's solution, or a 

 solution containing tincture of iodine, adding this until the iodine colour 

 is permanent.) Or (b) transfer for preservation to 10 per cent, formalin. 



Or (2) 10 per cent, formalin. In order to prevent contraction it is- 

 advisable to extend the tapeworm and keep it fixed by glass plates, or 

 wind the worm around a wide glass tube or bottle, and then fix it. 



Or (3) fix in hot alcohol. 



Staining. As under flukes. It is necessary to sacrifice portions of the 

 tapeworm for this purpose, cutting out, e.g., mature segments, so as to 

 study the topography of the genitalia. 



Clearing. As under flukes. To examine the hooks satisfactorily it is 

 best to cut off the head with a sharp knife and mount. A certain amount 

 of pressure is then advisable in order to view the hooks completely so as 

 to measure them. 



