640 



SCIENCE 



[N. S. YOL. XL VII. No. 1226 



vention is to paste a border of ordinary black 

 binding tape on tlie coated side before work 

 upon the slide is begun. This is an easy 

 method also of inhibiting any tendency to 

 write upon more of the slide than can be 

 shown upon the ordinary screen. 



Lancaster D. Burling 

 Geological Survet, 

 Ottawa, Canada 



celloidin-paraffin methods 

 The review of Apathy's^ celloidin-paraffin 

 method published in Science by S. I. Korn- 

 work the present writer chanced upon, al- 

 though actively interested between the years 

 1912-1915 in similar methods of imbedding 

 plant tissues. 



During research studies in plant anatomy, 

 bulbs of Cooperia Drumraondii were found to 

 be particularly troublesome material to im- 

 bed. The delicate scales contain starch, cal- 

 cium oxalate crystals and a mucilaginous slime 

 which may coagulate during killing and fix- 

 ation. These scales are attached to a base or 

 axis formed of parenchyma, it is true, yet of 

 parenchyma of an entirely different structure 

 from that of the scales. The difficulties en- 

 countered because of the included materials 

 plus the variance in structure of the bulb axis 

 and its attached scales caused a wide search 

 for a suitable imbedding medium. The choice 

 at last was a combination of celloidin and 

 paraffin, the advantageous qualities of which 

 can not be emphasized too strongly. As Dr. 

 Kornhauser points out, celloidin in contact 

 with the object prevents shrinkage of the 

 material on cooling and paraffin allows of 

 serial sections which can be readily spread on 

 the slide. Whether there are advantages or 

 disadvantages in Apathy's oil mixture I do not 

 know, having never tried it, but I do know 

 that entirely satisfactory results can be ob- 

 tained with material which can be handled 

 neither in paraffin, in celloidin, in agar-agar, nor 



lApittyj S., 1912, "Neuere Beitraege zur 

 Sehneidetechniek, " Zeitschr. wiss. Mikr., Bd. 

 XXIX., S. 449-515, 4 textfiguren. 



2 Kornhauser, S. I., ' ' Celloidin Paraffin 

 Method," Science, N. S., Vol. XLIV., No. 1134, 

 pp. 57-58, July 14, 1916. 



in rubber and paraffin, by a much more simple 

 celloidin-paraffin method than that of Apathy's. 

 The technique planned and followed out by the 

 present writer was simply as follows : Material 

 is treated to the celloidin process of imbedding 

 up to the point where the object would usually 

 be set in a block. Instead all surplus celloidin 

 is removed from the object which with the 

 adhering and infiltrated celloidin is hardened 

 in 70 per cent, alcohol and later placed for 

 clearing in chloroform for two hours. The 

 next step is to place the object in 85 per cent, 

 alcohol and from there on to follow the paraffin 

 method. Material thus treated cut with an 

 unusual smoothness, making it possible to ob- 

 tain serial sections 10 i" in thickness with an 

 ease that was a surprise and also a great com- 

 fort. 



If one desires to cut serial sections of objects 

 too large for the block of a rotary microtome 

 or to be handled in paraffin, such large ob- 

 jects imbedded in celloidin (mature bulbs) can 

 be cut into sections 50-75 /^ thick with the 

 sliding microtome, and placed immediately 

 in 70 per cent, alcohol, from which they can 

 be carried through the alcohols and imbedded 

 in paraffin. It seems probable that Apathy's 

 oil mixture would be a valuable asset here be- 

 cause in cases where it is necessary to retain 

 considerable celloidin, e. g., in handling bulbs 

 where the scales ordinarily fall apart on cut- 

 ting, it would prevent the shrinkage caused by 

 the drying effect of the alcohols and the heat 

 from the bath. 



There are surely two advantages to the 

 celloidin-paraffin method as commonly used 

 by the writer, (1) its simplicity and (2) the 

 removal of surplus celloidin, a substance af- 

 fected by the drying effect of the higher al- 

 cohols and heat and also inert itself in histo- 

 logical value and yet troublesome because of 

 its affinity greater than that of plant tissues 

 for stains such as gentian violet and safranin. 



Margaret B. Church 



alligators as food 



An article by the writer on " Reptiles as 

 Food," which appeared in the December, 1917, 

 number of The Scientific Monthly, having 



