BY S. J. JOHNSTON. 293 



cases, however, they are somewhat broader, especially those that 

 have a round rather than a flat cross-section. The whole is now 

 flooded with the fixing solution. I have obtained the best results 

 by using boiling sublimate acetic, or sublimate acetic alcohol — a 

 saturated solution of corrosive sublimate in water or 70% alcohol 

 respectively, with 2% glacial acetic acid added These solutions 

 used cold, and Flemming's strong solution also give good results. 

 In a few seconds, the little bottles arc lifted off for a moment, 

 when it may be seen, by the opacity of the tissues round the 

 edges, tliat the fluid is already taking effect. In fi-om half a 

 miinite to two or three minutes, the whole body has become 

 opaque, and the bottle-weights may be removed, and the cover- 

 glasses washed t)ff by disturbing the fluid. The worms are now 

 left in the fixing fluid for from half an hour to two or three hours, 

 and then treated in the way usually employed for the after-treat- 

 ment of tissues fixed in the fluid used, whichever it may have 

 l)een. 



Another method, which gave excellent results, for fixing the 

 worms for whole-mounts, suggested to me by my chief. Professor 

 Haswell, is this— a coverglass, with two little dabs of vaseline 

 near the edges, is inverted over a worm lying in a drop of salt 

 solution on a slide. By means of the dabs of vaseline, the pres- 

 sure on the worm may be made as little or as great (up to a 

 certain extent) as we please. In this way, the most delicate 

 worms do not become squeezed too much, while the larger ones 

 (of course no very large muscular flukes occur in frogs) are held 

 firmly enough in the required position till they are fixed. But 

 in this method, only cold fixing solutions, whicli do not act so 

 quickly as the hot, can be used. I have not found the spines or 

 processes of the cuticle injured bj' these reagents, as, for instance, 

 Stafford has(88), in using glacial acetic acid. 



In fixing the wox'ms for sections, after washing in salt solution 

 to remove slime, etc., the worms are allowed to come to rest in a 

 a little drop of salt solution in the bottom of a dish, and are then 

 flooded with a comparatively large bulk of fixing fluid. The 

 bcnling sublimate acetic kills them practically instantaneously, 

 and with the least amount of contraction; thu Flemming also 



