534 The American Naturalist. [June, 



the other hand, we wish to study osseous lamellae or stained prep- 

 arations, the section is first placed in a solvent of balsam, then trans- 

 ferred to a warm solution of balsam until the entire canalicular sys- 

 tem is filled, when it is mounted. 



Methods of Decalcification. — Thomas' Nitric Acid Method.' 

 — Pieces of fresh or hardened calcified tissue, bone, tooth, etc., are 

 placed in 9-V , alcohol until completely saturated, then transferred to 

 a solution consisting of five parts 95% alcohol and one part c.p. nitric 

 acid, in which they are left for several days. The liquid should be 

 occasionally shaken and renewed until the tissue is completely decalci- 

 fied. The process is very rapid, owing to the solubility of the pota.--ir 

 nitrate in weak alcohol. Very large pieces may be decalcified in from 

 two to three weeks. The object is then placed in a vessel of 95% 

 alcohol, to which calcium carbonate is added until there is a residue 

 of the precipitate. This mixture should also be occasionally Bhaken 

 and renewed. After several days litmus paper no longer shows an 

 acid reaction ; the object is left in the fluid a day or two longer, then 

 washed with a spray of alcohol, which removes the most of the 

 calcium carbonate deposited on the surface. The extremely fine par- 

 ticles remaining do not in any way interfere with the cutting. If one 

 wishes to avoid this deposition the object may be wrapped in filter 

 paper. This, however, requires a longer time for the removal of the 

 acid. By this method large pieces of very dense tissue are very rap- 

 idly decalcified and then completely freed from the acid ; the soft 

 parts undergo but little swelling, while the tissue stains as readily as 

 before decalcification. 



Hang's Phloroglucine Method. 2 — This is one of the most rapid dec- 

 alcifying agents ; the structures are perfectly preserved with the excep- 

 tion of blood, which is considerably changed. The introduction of the 

 method is due to Andeer, 2 who used the phloroglucine in combination 

 with hydrochloric acid, but with variable results. By substituting nitric 

 acid perfectly uniform results are obtained. The solution is prepared 

 by warming 1 g. phloroglucine in 10 c.c. of c.p. nitric acid. This must 

 he done slowly and carefully ; soon a dark ruby solution is obtained ; 

 to this is added 50 c.c. distilled water. If a larger quantity of the 

 fluid is desired 10 c.c. acid are added to every 50 c.c. of 

 the volume has reached 300 c.c, which is the limit of the protective 



,p. 191,1891. 



"• 



