1S{)3.1 MK'RoSCol'ICAL .lol'KXAL. 251 



it, (tvcr which ohjects are phiced, while over the hhuk paptr, 

 cte.. tlic ohjt'ct of course Itciiii,' oil a slide 



Ranvier's One-third Alcohol. — (1 part alcohol .'J<>'^ and 2 

 l»arts distilled water), is a dissociation liquid of the first order. 

 Tissues rich in cells are dissociated in it in 24 hours. The fix- 

 iiiL' and staining of the elements are then readily accomi)lislied. 



Iodised Serum. — Next to dilute alcohol iodised serum is most 

 iiii|iurtant. [Tiiis is made of the amniotic fluid of the sheep or 

 other animal and treated with iodine. It should be made in 

 lar<re quantity in a laboratory, and is omitted here as ])rol)ably 

 beyond the reach of those for whom these instructions are in- 

 tended]. 



Caustic Potassa. — In a strong solution (40 i)er cent), this is 

 excellent, Init the {jreparations can not be preserved nor stained. 

 Keep the bottle corked with a rubber stopper. The solution 

 is allowed to act on the object while on the slide. To separate 

 the elements it is often only necessary to press slightly on the 

 cover glass. 



Chromic Acid. — This is used in weak solution (1 to 5,000 of 

 wiiter). Tissues should remain in it for 2 or 3 days 



Dissociation by Partial Drying. — Place the tissue on a glass 

 plate, without liquid, and when partly dry, without being ad- 

 herent to the glass, divide it quickly with needles. If the tis- 

 sue is rich .in ctlls, like the the marrow of bones, excellent dis- 

 sociation may be had by little blows of the side of the scalpel 

 blade. Harden by osmic acid vapor, stain by picro-carmine, 

 and mount in glycerine. An indispensable condition is to oper- 

 ate ra))idly, before the drying is too far advanced. 



Dissociation in Liquid. — After a sojourn in the diluted alco- 

 h<»l or in iodised serum, dissociation of the tissue is easy By 

 curved scis.sors cut ofi'a small piece and place it on the slide in 

 a drop of the dissociating liquid. A slight agitation l)y the 

 forceps will free the cells. Add a drop of picro-carmine to the 

 dilute alcohol, mixing them with a needle, and add the tliin 

 cover. . . . Allow a drop of glycerine to run under. 



The following also gives good results: — Put a piece of tissue 

 in a glass tul»e with 10 c. c, of the h alcohol. In 24 hours, .shake 

 violently, and ))our out, the liquid with the separated cells, and 

 add jticro-carmine. Let it settle for 24 hours. When tlie cells 

 have fallen to the bottom pour otlmo^t of the tiuid, draw up with 



