510 SUMMARY OF CURKENT RESEARCHES RELATING TO 



asphalt or gold size. The latter may be obtained at the oilshop at nine- 

 pence the half -pint, or in smaller quantities at a similar rate. 



Paraffin Emheddinrj. — The specimens should be placed in fixing-fluid 

 (chromo-acetic) for eight or ten hours. They are then removed to a 

 tube containing water. This is changed several times during twenty- 

 four hours. The next process is to decant part of the water, and add an 

 equal part of alcohol to the water remaining. Allow to stand for six or 

 eight hours, or more if tissues are strongly resistant. The 50 p.c. alcohol 

 so formed is then replaced by 75 p.c. for five to six hours. This again is 

 followed by 90 p.c. for a similar time. Finally absolute is added, and they 

 may remain in this indefinitely. After the specimens have been fixed, 

 washed, and finally dehydrated, they are placed in xylol for twenty-four 

 hours. The next step is to place small pieces of the embedding wax 

 into the tube. The xylol dissolves this and slowly infiltrates the speci- 

 men with wax and xylol. This is continued for twenty-four hours. 

 The specimens are then removed to a beaker containing melted wax, 

 and remain at a temperature of 55° C. in a hot-water oven. If the 

 temperature is increased consideral)ly, shrinkage will most certainly 

 take place, so this must be guarded against with close attention to the 

 recording thermometer of the oven. The author has constructed a 

 small oven for this purpose by means of two square tins of different 

 sizes, one soldered into the other. The outside -tin contains the water, 

 and the inside acts as the water-oven. 



When thoroughly infiltrated, take a small Petri dish, and moisten 

 with dilute glycerin and warm in the oven. Now pour into the dish the 

 melted wax, and with a pair of heated forceps remove the specimens 

 from the beaker of melted wax and place them in the Petri dish. Now 

 gently place the dish on top of a filled basin of water, and still holding 

 the dish by thumb and forefinger, gently blow with the mouth across 

 the surface of the now setting wax film. "When this setting film has 

 well formed, rapidly sink the dish, and allow to remain for a few minutes 

 in the water. Now remove the Petri dish and gently raise the hardened 

 wax with a penknife. Taking the whole of the wax, carefully cut out 

 the specimens so that a fairly symmetrical block of wax is obtained in 

 each case, and finally trim to square prismatic form. The blocks are 

 now ready to affix to the object-holder of the microtome. 



The next step after fixing the block is to prepare the cleaned slips 

 to receive the ribbon section. This is done by slightly smearing the slide 

 with the finger-tip moistened with white of egg. This may be kept 

 permanently by adding 50 c.cm. of white of egg to 50 c.cm. of glycerin 

 and 1 gr. of salicylic acid. Next place the slips under water, and as the 

 ribbons are cut place a suitable piece of each on a slide removed from 

 the water. The ribbon now floats upon the remaining water on the slip. 

 Gently warm the sHp, and the ribbon will flatten out. Now drain ofi" the 

 water, arrange the section in the middle of the slip, and stand on its 

 edge to finally drain for half an hour. The slips, when brought to this 

 stage, are then allowed to dry in a temperature not above the melting- 

 point of the wax for twenty-four hours ; they are then ready for stain- 

 ing. This is usually done by hasmatoxylin, followed by a counter-stain. 

 The method adopted in the author's own case was as follows : — 



