BETZ'S METHODS. 391 



The preparation is now brought into a 3 per cent, solution of bichromate 

 of potash. (A small weight is attached to it to prevent any portion of it 

 from floating above the surface of the liquid. After a day or two it will 

 have lost much of its alcohol, and will sink to the bottom of the vessel, 

 which is equally undesirable ; this must be watched for, and the preparation 

 hung up or otherwise supported.) The vessel is put away in a cool place. 

 As soon as a brown turbidity is seen in the liquid, together with a brown 

 deposit on the preparation, the hardening may be considered to be complete/ 

 The preparation must be at once washed with water, and put away until 

 wanted in a to 1 per cent, solution of bichromate. 



Cerebellum. Must be quite fresh, and before placing in the iodine the 

 membranes and vessels must as far as possible be very carefully removed. 

 (If the pia mater does not come away freely, the organ must be macerated 

 for a few hours in iodine solution in which other preparations have been 

 kept, and which is diluted before using for this purpose.) The membranes 

 having been removed, the cerebellum is placed (supported on cotton wool, 

 with which the different organs are so propped up as to preserve their 

 natural position) in solution of iodine for two or three days, and fresh 

 iodine solution frequently added. 



The pia mater is now removed from the rest of the preparation, which is 

 put back for seven to fourteen days into the iodine solution. If at the 

 expiration of this time it be found that the cerebellum can be supported on 

 the finger by the vermiculus alone without bending, the preliminary harden- 

 ing is complete, and it is brought into a 5 per cent solution of bichromate, 

 where it remains until fit for cutting. 



Cerebrum. The cerebrum is divided into two halves along the median 

 line of the corpus callosum, and put into the iodine solution. After a few 

 hours the pia mater is removed from the fissure of Sylvius and from the 

 corpus callosum, and if possible the choroid plexus is removed likewise. 



The preparation is now put away in the iodine solution in a cool place 

 (in summer in a cool cellar), and fresh iodine added as soon as the liquid is 

 seen to lose colour (which must be watched for). After twenty-four to 

 forty-eight hours the remaining pia mater is carefully removed by means 

 of scissors and forceps from the fissures and convolutions, and one half- 

 volume of fresh iodine solution is added to the liquid. (To facilitate the 

 penetration of the liquid, wads of cotton wool are stuffed into the fissure 

 of Sylvius, between the operculum and the median [central] lobe, in the 

 direction of the descending cornu, and between the convolutions). After 

 twenty-four to seventy -two hours the brain is brought into fresh solution 

 of iodine in 70 per cent, alcohol, where it remains until the hemispheres are 

 hard enough to be supported on two fingers without bending. (This will 

 not be before ten to fourteen days.) It is then put into 4 per cent, solution 

 of bichromate and left to acquire its definitive hardness. If an excessive 

 brown deposit make its appearance, and the brain be found notwithstanding 

 to be not hard enough for cutting, it must be rinsed with water and the 

 bichromate solution changed. When ripe for cutting the brain ought to 

 show an almost equal intensity of yellow-brown stain over the whole surface 

 of a cut made through the total thickness of a hemisphere. 



