THE ORDINARY METHODS OF PREPARING TISSUES. 15 



acetic acid one part. It is said that by this method sections of 

 the cord may be made transparent in a few hours (Frey). 



Alcohol and acetic acid mixture (Moleschott). This ' ' strong 

 acetic acid mixture," of which the formula is strong acetic acid 

 (1.070 sp. gr.), 1 vol.; alcohol (.815 sp. gr.), 1 vol.; distilled 

 water, 2 vols., causes the connective- tissue substances to be- 

 come very transparent. Delicate textures do not tolerate it 

 well (Frey). 



Molybdate of ammonia has been recommended by Krause 

 for hardening specimens. It has met with some favor. 



Solution of osmic and chromic acids. Flesch recommends 

 a union of these acids for hardening and decalcifying bone. 

 It is also useful for hardening other tissues. His formula is 

 as follows : osmic acid, 10 parts ; chromic acid, 25 ; aq. destill., 

 100. 



Alcolwl and acetic acid and muriatic acid solution. 

 Beale gives the following formula: water, 1 oz. ; glycerine, 1 

 oz. ; spirit, 2 oz. ; acetic acid, 2 drachms ; hydrochloric acid, 

 drachm. This is said to harden well and be suited for epithe- 

 lial structures (Frey). 



Method of hardening the brain. Hamilton recommends 

 the following method : pieces of brain and cord cut into sec- 

 tions not more than an inch in length, or length and breadth, 

 are immersed in a fluid containing three parts of Miiller's fluid 

 and one of methyl alcohol, and put away for some three weeks 

 in a refrigerator. Then they are to be soaked in a solution of 

 the bichromate of ammonia (1-400) for a week ; another week 

 in a solution of 1-100 ; a third week in a solution of 1 to 50; 

 and finally kept in chloral hydrate (12 gr. to the ounce). Be- 

 fore cutting, they are to be washed twelve hours or more in 

 water ; they then are to stand forty-eight hours in a syrup 

 containing two parts of refined sugar to one of water. He then 

 cuts with Rutherford's microtome. Staining is done with 

 osmic acid and carmine. 



For clarification he uses oil of cloves or turpentine. 



How to embed specimens. When a piece of tissue is so 

 small that it cannot be held in the hand, it is customary to 

 embed it in some substance of about the same consistence. A 

 combination of wax and oil answers the purpose very well ; 

 they should be mixed in about equal proportions in a porce- 

 lain dish, and then heated together until the wax is thoroughly 



