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VI. — The Preparation of the Brain and Spinal Cord for 



Microscopical Examination. By H. S. Atkinson. 



(Read before tJie Medical Microscopical Society, May 16, 1873.) 



The few remarks which I propose to bring before your notice this 

 evening are based upon the results of some experiments which I 

 performed last summer, in the Physiological Laboratory, King's 

 College, by desire of Professor Eutherford, the object of the experi- 

 ments being to ascertain the best method of staining preparations 

 of the brain and spinal cord, previously hardened in chromic acid. 



It may be interesting to some few of you here to night to know 

 the method of preparing the brain and spinal cord for microscopical 

 examination, and therefore, with your kind indulgence, I propose to 

 give an account, as briefly as possible, of the method of preparing 

 those tissues ; first, when hardening fluids are used ; and secondly, 

 when hardening fluids are not used, but the tissue examined 

 at once. I desire you to understand, however, that my knowledge 

 of these methods is derived from instructions received from Pro- 

 fessor Eutherford, and that I have no claim to any of the points to 

 which I would direct your attention, excepting the method of 

 staining the sections. 



Fu'st, with regard to the preparation when hardening fluids 

 are used. 



I thuik it best to treat this division of my subject under four 

 different heads, as you may be better able to follow the somewhat 

 complicated directions which I shall be obliged to lay before you. 



First, as to the hardening of the tissues. 



/Secondly, as to the cutting of the tissues. 



Thirdly, as to the staining of the tissues ; and 



Fourthly, as to the mounting of the tissues. 



First, as regards the hardening of the tissues. 



The method which is found best is as follows : — 



The fresh tissue, that is cord and brain, is cut into pieces as 

 smaU as convenient, and placed for twenty-four to forty-eight 

 hours in methylated spirits of wine. This prevents it from 

 " rotting." It is then placed in the " hardening fluid." For the 

 spinal cord, a solution of chromic acid of ;j to ^ per cent, in water 

 answers best. If the cord be small, as that of a cat or rabbit, a 

 ^ per cent, solution is strong enough ; but if the cord be larger 

 than that, as that of the ox, or man, a \ per cent, solution must 

 be used. 



For the cerebrum and cerebellum, a mixture of chromic acid 

 1 part ; potassium bichromate, 2 parts ; water, 1200 parts, is best. 



From four to six weeks are necessary for the chromic acid to 

 render the nerve tissue sufficiently hard. It may then be cut ; or if 



