100 PRACTICAL PARASITOLOGY 



fresh liquid, after quickly removing what is left of the original appli- 

 cation ; this manoeuvre should be repeated until the entire worm 

 becomes opaque. It must be borne in mind that the lifting of the 

 cover-glass is very liable to tear the specimen, especially when the 

 preparation has been subjected to pressure. Should this appear 

 imminent, the cover-glass should be allowed to fall back into place 

 and fresh liquid must be added at the edge of the glass until the 

 cover-glass floats, either quite free or with the worm attached. In 

 either case the specimen will be left exposed, either upon the glass 

 slide or the cover-glass, and the process of fixing may be completed 

 by adding fresh fluid. Or the worm may be freed from the glass by 

 pouring the Hofer mixture over it ; it should then be transferred to 

 a watch-glass by means of a fine brush. If the object is fixed upon 

 the glass slide, as soon as it becomes opaque it should be washed off 

 into a watch-glass, and it should, in any case, be allowed to remain 

 for a short time in the fixing fluid. The fluid is then removed by 

 means of a pipette and clean water is added. This is quickly drawn 

 off and replaced by 45 to 50 per cent, alcohol. The object should 

 remain for a few minutes in the alcohol, which is then drawn off 

 and replaced by 70 per cent, alcohol. This alcohol is changed every 

 few hours until it ceases to contain picric acid, i.e., until it no longer 

 acquires a yellow colour. The process may occupy several days. The 

 object is next put into 80 per cent, and afterwards into 96 per cent, 

 alcohol, and in this stage may be kept for any length of time. Speci- 

 mens should be stored in closely covered jars ; or they may be put 

 into glass tubes and closed with wadding (not cork) ; or into glass 

 bottles with well-fitting glass stoppers. They should be carefully 

 labelled, the description including the name and pedigree of the 

 host, the organ from which the parasite was taken , method of 

 treatment, date. 



Eoundworms and muscular flatworms may be prepared whole in 

 the following manner. The worms should be cleansed and put into 

 a watch-glass containing a small quantity of normal saline. Warm 

 saturated watery solution, or warm alcoholic solution, of mercuria 

 chloride should be poured over them and the objects allowed to remain 

 in soak until they become opaque, which will be in a few minutes. 

 If the watery solution is used they should be rinsed in normal saline, 

 but in 70 per cent, alcohol if the alcoholic solution is used. In either 

 case, a few drops of tincture of iodine should be added to the rinsing 

 fluid to remove superfluous sublimate from the tissues, and the liquid 

 should be changed until it ceases to lose its colour. Objects washed 

 out with normal saline are treated with alcohol of gradually increasing 

 strength and may be stored in 95 per cent, alcohol. Objects rinsed 

 in alcohol are put straight into 80 per cent, and afterwards transferred 



