ALCOHOL HARDENING 21 



a part is severed from the influences which control the complete 

 organism. 



From what has been said, we appreciate the necessity of agents 

 which, when applied to portions freshly removed from the animal, 

 or even before removal, shall instantly stop all physiological pro- 

 cesses and retain the elements in permanent fixity. 



Very much of the human structure which is available will be 

 secured only after functional activities have long ceased, and the 

 structure essentially altered. We are, therefore, compelled to 

 resort to the use of material from the lower animals in very many 

 instances. 



ALCOHOL HARDENING 



The tissue, whatever process may be in contemplation, having 

 been removed from the body as quickly after death as possible, 

 should, with a sharp scalpel, be divided into small pieces. Of the 

 more solid organs, pieces not more than one -half to one centimeter 

 thick will be sufficiently small, and they will harden rapidly. The 

 smaller the pieces and the larger the quantity of hardening fluid, 

 the more quickly will the process be completed. The volume of 

 fluid should exceed that of the tissue at least twenty times. Wide- 

 mouthed, well stoppered bottles, from one ounce to a pint, or even 

 larger, are best, and they should be carefully labelled and kept in 

 a cool place, with occasional agitation. 



Quick Method. A piece of any solid organ, say liver, spleen, 

 pancreas, kidney, uterus, lymph -node, etc., not more than one -half 

 centimeter thick, may be perfectly hardened in twelve hours by 

 immersion in one ounce of ninety -five per cent, alcohol. No more 

 should be thus prepared than is to be cut within twenty -four 

 hours, on account of the shrinkage which results after the pro- 

 longed immersion of solid structures in strong spirit. 



After the tissue has been one hour in the above, it may be 

 hardened in one or two hours more if transferred to absolute 

 alcohol. This method is of frequent advantage in pathological 

 histology. 



Ordinary Method. Generally it is better to place the pieces of 

 tissue first in eighty per cent, alcohol, and to transfer them after a 

 few hours to ninety -five per cent, alcohol, in which the hardening 

 is completed. In this manner the shrinkage and the extreme 

 hardening of the surface, which result when strong alcohol alone 

 is used, are avoided. The jar needs to be shaken occasionally. 



