462 NOTES AND MEMORANDA. 



remove the acid, into 70 per cent, alcohol, where it is to remain five 

 or six hours. From this it is to be removed into 90 per cent, 

 alcohol, which is to be changed until the yellow tint has either 

 disappeared or greatly diminished. Alcohol of 90 per cent, is better 

 than absolute for preserving the more delicate structures for a long 

 time uninjured, and for keeping the preparation at the proper degree 

 of hardness. 



For colouring, crystallized hsematoxylin is to be used, dissolved in 

 the following mixture : — Prepare a saturated solution of calcium 

 chloride in 70 per cent, alcohol, with tlie addition of a little alum ; 

 after having filtered, mix a volume of this with from six to eight 

 volumes of 70 per cent, alcohol. At the time of using the liquid 

 pour into it as many drops of a concentrated solution of hfema- 

 toxylin in absolute alcohol as are sufficient to give the required 

 colour to the preparation of greater or less intensity, according to 



This mixture, notwithstanding its chemical irrationality, gives 

 good results. Aqueous solutions, especially when they contain traces 

 of ammonia, are to be avoided, since they are very hurtful to many 

 delicate tissues. The object must remain in the dye for a period 

 varying from a few minutes to six hours, according to its size and to 

 the nature of the tissues composing it. It is a good rule, when 

 intending to make sections, to stain deeply and to cut them very thin. 



When removed from the dye the preparation is to be washed in 

 90 per cent, alcohol, in which it may remain from six to twelve hours. 

 Finally, to remove every trace of water, it should remain for half or a 

 whole day in absolute alcohol. 



If the preparation is to be cut it must be removed from absolute 

 alcohol to essential oil of bergamot, in which it should remain for 

 some hours, in order to fit it for being imbedded in paraf&n, which is 

 removed from the sections when cut by means of a mixture of four 

 parts of essence of turpentine with one part of kreosote. Finally, 

 the sections are mounted in resin dissolved in essence of turpentine. 



Histologists are warned not to use a solution of resin in alcohol. 

 The preparations mounted in this are at first beautiful but soon 

 become spoiled, in consequence of the precipitation of crystals or of 

 an amorphous substance. He lost in this manner many hundreds of 

 preparations, and the same results have occurred in the Zoological 

 Station at Naples. 



Preparation and Preservation of the Lower Organisms. — M. 

 Eaphael Blanchard, of Paris, referring to the process employed by 

 Koch to preserve and photograph Bacteria,* saysf that more than 

 two years ago, he preserved Bacteria in lasting preparations by using 

 with excellent results osmic acid instead of the process of desiccation 

 employed by Koch, which he considers a very bad one. 



In a few hours, or two days at the longest, the surface of water in 

 which an organized substance (vegetable or animal tissue, &c.), has 

 been macerated, becomes, as is well known, covered with a slight 



* See this Journal, i. 195. f ' Rev. Intemat. Sci.,' iii. (1870) 24.5. 



