108 THE MICROSCOPE 



section is rinsed in water, and loses some eosin ; it is then laid in 

 a watch-glass wdth a solution of one of the other colours and allowed 

 to remain some minutes, till it is coloured very deeply, almost black. 

 Rinse again in water, and then place in alcohol, which dissolves both 

 the colours if not carefully watched. This is in my opinion the 

 most critical part of the process : — i.e. hitting the right moment 

 when both the colours have been sufficiently drawn out. A good 

 plan is to take a section out and view it in oil of cloves under the 

 microscope ; if found too deep, replace it in alcohol. In general, 

 it is better to remove the preparations when still too blue, as the 

 eosin is drawn out somewhat quicker than the other colours. The 

 oil of cloves, in which the preparations are put after the alcohol, 

 does not affect the eosin, whilst it dissolves the other colours. Any 

 desired relation between the colours can be thus obtained. When 

 stained as required, the oil of cloves is withdrawn as completely as 

 possible by blotting paper (the best plan I find is to lay the paper 

 on one side of the preparation on the stage and place it slanting). 

 Then apply Canada balsam in Benzole or Chloroform. If too much 

 oil of cloves is left behind, a further extraction of the blue takes 

 place, and the object is surrounded by a blue halo. The skin, 

 nails, hairs, muscular tissue, bones, cartilages, nerve system 

 (though not good for the peripheral nerve system), are finely dis- 

 played. Methyl violet, but not the other colours, stains the fine 

 nerves in the skin of the lamprey very beautifully. The alimentary 

 canal, glands aquiparous and muciparous, in the root of the 

 tongue, glands sub-maxillary and sub-lingualis, parotid, pancreas 

 (the lachrimal have most peculiar red cells). The epithelium of 

 mouth, tongue, and oesophagus separate on being stained in the 

 superior and inferior layer ; the epithelium, glands of stomach, 

 and intestines are excellently adapted for this staining. 



Purpurin : — Take about as much as will lie on the point of a 

 pen-knife, boil in 50 cc. of glycerine, (it may either be concentrated 

 or have a litde water added to it), allow to stand for two or three 

 days, and then filter. Unlike Ranvier's solution, it may be kept 

 months without precipitation; it is quite permanent when mounted 

 in Canada balsam and benzole, or glycerine slightly acidulated. 



A simple and speedy method of staining Animal and Vege- 

 table sections : — After cutting sections, wash them in water and 



