142 PRACTICAL HISTOLOGY. 



the case of the bloodvessels an immersion for a fort- 

 night or three weeks in a 1 per cent, solution of 

 bichromate of potash answers best ; the pieces are 

 then placed for a day in weak spirit, and finally 

 transferred to strong methylated alcohol. Here they 

 may remain without detriment until it is convenient 

 to prepare the sections. 



The method of cutting and preparing sections for 

 the microscope is in the main the same for nearly all 

 the tissues and organs of the body, and since, in the 

 further study of these, it will be in almost constant 

 requisition, it will be convenient to give in this 

 place an account of the mode usually adopted, re- 

 serving any special modifications which it may be 

 needful to make in the preparations of particular 

 organs until these come to be treated of. 



METHOD OF PREPARING SECTIONS. 



Preparation of an embedding mass. Unless 

 the piece of tissue is large enough to admit of being 

 held firmly by the left hand while sections are made 

 with a razor held in the right hand, it is necessary 

 to support it in some way. This is usually done by 

 surrounding it in a mould with some fatty mixture 

 which requires only a moderate temperature to melt 

 it; the mixture or mass should, when cold, be of 

 about the same consistence as the hardened tissue. 

 Perhaps the most generally useful mixture for this 

 purpose is one of wax and olive oil. This can, by 

 varying the proportions of the ingredients, be suited 

 at will to the consistence of the tissue which it is 

 desired to obtain sections of. For most purposes the 

 following is the best proportion to adopt, and it is to 

 be observed that whenever subsequently the "wax- 

 mass" is mentioned, this particular mixture is indi- 

 cated : Sixty cubic centimetres of olive oil are poured 

 into a measuring-glass, and small lumps of white wax 

 are added to the fluid until it occupies a hundred 

 cubic centimetres. It is now placed in a porcelain 



