and Laboratory Methods. 2728 



through the carotids. The head was put into a wooden box just large enough 

 to hold it and the box was filled with gum solution. The closed box was kept 

 in the freezing mixture until well frozen. The box was then fixed in a frame 

 and sawn across along with its contents. The sections so obtained show extremely 

 little displacement or distortion of the parts of the brain. r. p. 



A Method of Preparing the Membranous Dr. A. A. Gray describes in the Jour. 

 Labyrinth. ^nat. and Physiol., N. S., Vol. 17, 



Part IV, a method of making demonstration specimens of the membranous 

 labyrinth of the human ear. Since it is a much neater method than any before 

 described and will be found applicable in the case of small mammals, an account 

 of it is given here for the benefit of Journal readers. The principle of Dr. 

 Gray's method is to embed the whole pyramid of the temporal bone so thoroughly 

 that no acid can affect the soft parts, then to decalcify and disintegrate the bone 

 so completely that no force whatever is required to remove the destroyed tissue 

 surrounding the labyrinth, and finally to remove the embedding material in such 

 a way that the membranous labyrinth is left uninjured. 



The pyramid of the human temporal bone is removed from the base of the 

 skull in the post-mortem room. The superfluous bone is removed with a saw ; 

 the stapes is carefully extracted from the oval window and a small hole is filled 

 in the superior semicircular canal. The structure is then immersed in 00 per 

 cent, alcohol for at least a fortnight, the alcohol being frequently changed. It 

 is then transferred to absolute alcohol, where it remains at least a fortnight, this 

 alcohol also being frequently changed. During this period it must be kept in a 

 glass stoppered jar. From absolute alcohol the bone is removed quickly to 

 xylol, where it again remains at least a fortnight, the xylol being frequently 

 changed. If a vacuum be made in the jar above the liquid at intervals, diffusion 

 occurs more rapidly and completely. From the xylol the bone is removed to 

 melted parafBn of a melting point of 52° C. or 54° C. The paraffin must be 

 changed two or three times during the fortnight which must be allowed for the 

 embedding. This is important to the success of the method ; the paraffin must 

 permeate the soft parts far more completely than is necessary in the case of 

 embedding for microscopic sectioning. A vacuum may be made above the par- 

 affin, which will sometimes solidify during the process ; this, however, does not 

 appear to affect the ultimate result. Of course the temperature of the paraffin 

 bath must not be allowed to rise above 55 or 56° C. After the bone has been 

 in the paraffin bath for a period ranging from two to three weeks, the paraffin is 

 cooled as quickly as possible and the bone cut out from the block. The super- 

 fluous paraffin is then carefully scraped off the bone and decalcification is pro- 

 ceeded with. For this purpose neither nitric nor hydrochloric acid by itself is 

 suitable. They should be mixed. The best solution consists of 2 parts of nitric 

 acid to 3 parts pure hydrochloric acid, and 6 to 18 parts water; the nitric acid 

 should be mixed with the water first, and the hydrochloric acid added. The 

 bone is put into a large quantity of this mixture and suspended near the top by 

 fine twine. The mixture should be frequently changed, and in about three weeks 

 or a month decalcification and disintegration will be complete. It will be found 



