22 



Special Methods for Parasitic Worms. 

 Nematodes. 



After washing thoroughly as above directed,'"' kill by plunging 

 each separately into a quantity of hot 70 per cent, alcohol. A 

 temperature of 50^-60^ C. is high enough. 



(N.B. — Care must be used, as the vapour given off is highly 

 inflammable.) The advantage of this method is that the worms 

 should die in a straight position. 



After being killed in this way the worms are to be stored in 

 fresh 70% alcohol (never in formalin). 



Trematodes. 



After the first shaking up in salt solution the dirty liquid is 

 poured off, and a small quantity of fresh salt solution introduced. 

 The worms are shaken vigorously in this, and an equal quantity 

 of saturated solution of corrosive sublimate added quickly, the 

 shaking being then continued for several minutes. This should 

 kill and fix the worms in an extended position. They may be left 

 in the fluid for several days, or transfeiTed at once to water, in 

 which, in any case, they should be washed for about twelve hours. 

 After this they may be stored in 70% alcohol as usual. 



[Formalin may be used instead of corrosive sublimate, in a 

 solution of 10% strength, followed by a weaker solution (about 3%) 

 as a storing fluid.] 



Cestodes. 



Wash gently in salt solution ;| then fix in a solution containing 

 equal parts of saturated corrosive sublimate and 70% alcohol, to 

 which add a few drops of glacial acetic acid — the whole heated 

 to about 50° C. The Tapeworms should remain in the fixing 

 fluid till it is cold ; they are then washed gently in running 

 water for twelve hours, and stored in 70% alcohol. 



PACKING OF SPECIMENS. 



The separate small bottles containing worms should be filled 

 as full as possible with the preserving fluid (alcohol or formalin), 

 and damage to the specimens by shaking prevented as far as 

 possible by a light packing of cotton -wool or tissue-paper. Care 

 must, however, be taken to insert the wool in such a way that the 



* In the case of Nematodes with a mouth-capsule, a thorough shaking-up 

 is necessary to remove parts of the tissues of the host, or other cWbris, from it. 



t When the Tape-worms are long and tend to become much tangled they 

 should be washed in a shallow dish, and picked out one by one on a splinter 

 of wood (not a metal instrument) and transferred to the fixing fluid. 



