8 BULLETIN 69, UNITED STATES NATIONAL MUSEUM. 



off and place in a shallow dish of salt solution portions of the intestine 

 to which the worms are attached, and by careful manipulation with 

 the back of a scalpel blade cause them to release their hold. In the 

 tall vessel of salt solution the tapeworms and more or less ingesta 

 will sink to the bottom within a few minutes. It is well to break up 

 the masses or clumps of material which sometimes float on the sur- 

 face of the salt solution in order to dislodge any worms which may be 

 entangled there and thus give them opportunity to sink. When suf- 

 ficiently settled, the top of the liquid should be poured off until the 

 layer at the bottom containing the tapeworms is reached. The vessel 

 is then filled up again and the liquid stirred a little and allowed to 

 settle as before. This operation is repeated until the fluid is no 

 longer cloudy when agitated. The tapeworms and such ingesta as 

 may be remaining at the bottom are poured out with a sufficient 

 amount of liquid into a shallow flat-bottomed glass dish, for example, 

 a petri dish of suitable size. The worms may now be readily seen 

 by placing the dish over a dark background, and may be picked out 

 by means of a dissecting needle, splinter of wood, etc., or, if very 

 small, by the use of a pipette. It is advisable, in order that very 

 small forms msij not be overlooked, that the contents of the dish be 

 carefully examined with a lens. If the worms are small and very 

 numerous, they may be poured with the ingesta and the supernatant 

 liquid into a beaker, as much of the salt solution as possible removed 

 by pouring or by drawing off with a pipette, and the killing solution 

 then added. Otherwise it is better to pick out the worms from the 

 ingesta and put them into a dish of clean salt solution, which may be 

 drawn off and replaced several times in order to free the worms from 

 mucus and adherent foreign particles. 



A very satisfactory killing solution is a mixture of equal parts of 

 70 per cent alcohol and saturated aqueous solution of corrosive subli- 

 mate, to which, after mixing, about 1 per cent of glacial acetic acid is 

 added. This mixture may be employed cold, but acts better when 

 heated to about 70° or 80° C. A liberal quantity should be used. 

 The worms may be lifted into the killing solution one by one on a 

 wooden splinter (metal should not be used on account of the action 

 of the corrosive sublimate, which will cause the worms to blacken 

 where touched by the metal), or they may be dumped into the killing 

 reagent together with the least possible quantity of salt solution, or 

 the process may be reversed and the killing reagent poured on the 

 worms after as much of the salt solution as possible is drawn off. 

 When the worms are long and liable to tangle and twist into knots, 

 the first method is preferable. Occasionally the worms, if very active, 

 get into this condition in the salt solution, and require to be disen- 

 tangled before fixation. This may generally be accomplished with 

 the aid of a couple of dissecting needles. 



