87 



or more, according to size, were then thoroughly washed in 70 

 per cent, of alcohol, until all the chromic acid disappeared, then 

 transferred to methylated alcohol, and finally to absolute alcohol. 

 The tissues were then treated in two ways. 



(1) The pieces of tissue were transferred to the stained fluid, a 

 strong solution of haematoxylin in Kleinenberg's solution. They 

 were left in this for a few days, and were then successively washed 

 in 70 per cent., 90 per cent., and 100 per cent, of alcohol. They were 

 left in absolute alcohol for twenty-four hours or more, until thoroughly 

 dehydrated. When perfectly free from water they were transferred 

 to turpentine for about forty-eight hours, and were then placed 

 in soft melted paraffin wax for about twenty-four hours and were 

 finally transferred into hard paraffin wax, where they were left for 

 about two days. The melting point of the hard wax was 59° C, of the 

 soft 49^" to 50° C. The tissues were then embedded in small square 

 blocks of the hard paraffin wax, and very thin sections cut by 

 means of the microtome. The ribbons of sections were cemented 

 to the slide with a solution of shellac in creosote, and mounted 

 at once in Canada balsam. 



(2) The preparation of the tissues was the same as above except 

 that the staining was left out until the sections had been cut and 

 cemented to the slide. The ribbons of sections were cemented to the 

 slide with a solution of white of egg and glycerine. The paraffin wax 

 was melted by placing the slide on a water bath, and was then 

 washed ofl" in turpentine. The slide was then placed in absolute 

 alcohol, to get rid of the turpentine, and afterwards transferred to 

 the staining solution. All these operations are best performed in 

 small beakers, containing the various solutions used. The best stain- 

 ing solution was found to be a dilute solution of Kleinenberg's 

 haematoxylin in water. This was made by adding a few drops of 

 a strong haematoxylin solution to a beaker of water until the whole 

 was decidedly coloured. The sections were left in this until they were 

 considerably overstained, and were then placed in a dilute solution 

 of acid alcohol to reduce the stain. The. acid alcohol solution 

 was only just strong enough to reduce the stain slowly. It was 

 made by adding a few drops of strong hydrochloric acid to a beaker 

 of 70 per cent, alcohol. The sections were then successively 

 washed in 70 per cent., 90 per cent., and 100 per cent, of alcohol, 

 and were next transferred to turpentine until quite clear and 

 transparent (a few minutes was found to be sufficient for this), 



