354 The Microscope. 



This operation of injecting will demonstrate the presence of 

 valves (s) in the canals at the caudal part of each proglottid or 

 segment of the worm. 



Thus it is that only that portion of the excretory system caudal 

 of the insertion of the canula will be injected, the valves (s) preventing 

 the flow cephalad. The worm, after being injected, is then washed 

 in water and put into a 75 per cent, glycerine, to which has been 

 added a few drops of acetic acid. In the course of a few hours the 

 worm will become transparent, and in addition to the excretory 

 system, the uteri {u), the ovaries (o), vagina (v), and vas deferens 

 (v d), which change but little if at all, will be distinctly seen. If a 

 worm or a portion of it thus treated be suspended in a bottle of 75 

 per cent, glycerine so as to be easily seen, and the bottle thoroughly 

 corked, the specimen will keep indefinitely. A tape- worm thus pre- 

 pared is, indeed, a beautiful as well as instructive object. 



For microscopical purposes, about five centimetres of the worm 

 treated the same as for the museum was mounted in glycerine jell}- 

 in a cell in the usual way. Another portion had the uteri {u), and 

 ovaries (o) of several of the segments also injected. The opera- 

 tion of injecting the uteri and ovaries is very simple, and is readily 

 accomplished by forcing the canula (b) further in than in the case of 

 injecting the excretory system, so that the canula reaches nearly the 

 the center of the segment. Occasionally the uteri can be injected 

 by forcing the canula but a little way into the vagina {v). 



Segments in which the uteri are fully developed and extented 

 with ova, need not be injected, as they are quite distinct; but the 

 ovaries and the miniature uteri are not seen well unless injected. A 

 few centimetres of the worm in which the excretory system is 

 injected with one color and the uteri with another, form very beautiful 

 preparations. 



Another preparation for the microscope was made by placing a 

 few segments of the worm in Miiller's flj^iid for three days, after 

 which it was injected, both the excretory system and the uteri (for 

 unless the uteri are injected they will not be seen in this prej^ara- 

 tion), then hardened in 50, 75, 95 per cent, alcohol, cleared in 

 turpentine 3 parts, carbolic acid 2 parts, and mounted in balsam. 

 These preparations in balsam require moi'e work than those in 

 glycerine, but it may pay in the future, and the greater permanence 

 compensates for the extra labor. 



