No. I.] SENSE-ORGANS OF LUMBRICUS AGRICOLA. 1 95 



hol, cedar oil, soft paraffin, one-half hard and one-half soft 

 paraffin, and finally embedded in the latter. Each change from 

 one reagent to another must be made gradually, and the tem- 

 perature of the paraffin bath must not rise above 54° C. The 

 minute structure of the sense-organ does not show well in 

 sections cut over \o\i thick. 



The serial sections are straightened out and fixed to a slide 

 by the alcohol method. The paraffin is then dissolved in tur- 

 pentine, and the sections run back into 70% alcohol. They are 

 then stained for about twenty-four hours in a weak solution of 

 Kleinenberg's haematoxylin, prepared according to the formula 

 given in Lee's Vade Mecum. It has been found best to mix 

 the stain about twenty-four hours before using, to use a weak 

 solution, and stain on the slide. When the sections are stained, 

 they are washed in 70% alcohol and then with a saturated solu- 

 tion of sodium bicarbonate in 70% alcohol. If overstained, 

 they may be treated with weak acid alcohol before using the 

 bicarbonate. The sections are then run into absolute alcohol, 

 cleared in clove oil, and mounted in xylol-balsam. 



The silver nitrate method used is, in general, that given by 

 Dr. C. J. Huber in Anat. Anzeiger, Jahrg. 7 (1892), p. 587, 

 Dr. Huber kindly suggested two changes which add to the per- 

 manence of the preparations : first, to leave the turpentine 

 on fifteen minutes instead of five ; second, to use pure balsam 

 instead of turpentine-balsam. At the suggestion of Professor 

 Reighard the creosote was replaced by cressylic acid, which is 

 less disagreeable to handle. Care must be taken to remove all 

 traces of the creosote or cressylic acid, otherwise the sections 

 are sure to spoil. For sectioning, pieces of the worm are 

 fastened to a wooden block which can be clamped into the 

 object-holder of a sliding microtome. The end of the block is 

 covered with thin collodion ; the object is taken directly from 

 the silver nitrate, in which it can be left until needed, pressed into 

 the collodion, and then covered with a few drops of the latter. 

 If exposed to the air, the collodion will soon harden so as to fix 

 the object firmly in place. It is well to moisten the collodion 

 over the tissue with a little 96% alcohol to keep it from con- 

 tracting the tissues while it is hardening. When the sections 



