856 



SCIENCE 



[N. S. Vol. XL. No. 1027 



time to make tie proper orientation of the ob- 

 jects to be embedded. The paraifine fre- 

 quently sticks to the glass unless considerable 

 care is taken to keep it absolutely clean and 

 to smear it carefully with glycerine or albu- 

 men fixative. Metal and porcelain dishes have 

 the same likelihood of sticking, but are other- 

 Vfise excellent. 



The author owes to Dr. Hally D. M. JoUi- 

 vette the suggestion that has led to our pres- 

 ent laboratory practise. Her original sugges- 

 tion was to make handmade trays of plaster of 

 paris. This was tried with excellent results 

 except that the trays break very easily. This 

 led the author to seek for a substitute that 

 would retain the advantages of plaster of paris 

 but would be less fragile. After a number of 

 experiments it was found that dishes made of 

 the same sort of unglazed earthenware as 

 flower pots answer all the requirements. 



The advantage of these earthenware dishes are 

 that they can be dipped in water until thor- 

 oughly saturated so as to be entirely impervi- 

 ous to paraffine. Danger of sticking is thus 

 entirely obviated unless one carelessly over- 

 heats them. If the water is driven out by 

 heating, the paraffine, of course, penetrates the 

 porous clay and renders the dish useless until 

 it has been dissolved and completely removed. 

 I have found that the best results can be 

 achieved in handling large quantities of mate- 

 rials by keeping the dishes in a vessel of water 

 a few degree warmer than the melted paraffine. 

 When one is wanted, remove it from the warm 

 water to a position on the warming stand that 

 will prevent its cooling off too rapidly. The 

 objects can then be oriented at one's leisure. 

 To cool the paraffine set the tray of melted 

 paraffine in a dish of cold water until hard 

 enough to immerse. As soon as the cake has 

 hardened it will float out without any difficulty. 



II. TURPENTINE AS A LABORATORY REAGKNT 



The waste of expensive laboratory reagents 

 by elementary students, who do not know their 

 value, is oftentimes a considerable annoyance 

 to the instructor in histology or other subjects 

 where students must be allowed more or less 



ready access to the stock room. Aside from 

 waste the economy of reagents is a matter of 

 no inconsiderable importance to the directors 

 of most laboratories. Such considerations as 

 the above have influenced us in trying various 

 experiments in substitution. 



Commercial turpentine, such as is sold by 

 the hardware store to painters, has been found 

 a valuable substitute for other much more 

 costly reagents. In fact, for many purposes it 

 is superior to the much more expensive article 

 purchased from the chemical-supply house. 



Most laboratories use turpentine for dis- 

 solving the paraffine after the ribbons have 

 been fixed to the slide. Wbile this usage is 

 comparatively widespread the practise of using 

 it in place of xylol, oil of bergamot, etc., for 

 clearing preparatory to embedding in paraffine 

 appears to be less frequent. After much ex- 

 perience with these various reagents the 

 author is convinced that it is not only vastly 

 cheaper, but that it is on the average quite the 

 equal of any of the others. It penetrates 

 freely and dissolves proportionally as much 

 or more paraffine. The specimens of plant 

 materials clear readily, infiltrate quickly, and 

 cut as well as if embedded through other re- 

 agents. 



I have found it actually superior to other 

 reagents in clearing sections. It clears readily 

 from 95 per cent, alcohol and so avoids the 

 use of absolute alcohol. Both time and ex- 

 pense are saved in this way. Slides and sec- 

 tions should, however, be rinsed in xylol before 

 being mounted in balsam. Some stains are 

 soluble in turpentine and so slides must not 

 be left overlong in it unless they are over- 

 stained. It is valuable in reducing overstain- 

 ing from analine blue and bismark brown. 



The ease and convenience of handling wood 

 sections and celloidin sections in which it is 

 desirable to retain the celloidin is an enor- 

 mous convenience. Sections can be trans- 

 ferred to turpentine from 95 per cent, alcohol. 

 In the former one step in the process is saved 

 and in the latter the danger of dissolving or 

 softening the celloidin is avoided. 



Lance Burlingame 



STANFORD' UNIVEKSITT, CAL. 



