16 ' THE METHOD OF MAKING POST-MORTEM EXAMINATIONS. 



are to be examined for fractures, inflammatory lesions, and tumors. In 

 cases of acute purulent meningitis, the temporal and frontal bones should 

 be carefully examined, as the inflammatory process is sometimes trans- 

 mitted from the internal ear, or mastoid cells, or frontal sinuses. 



The eyes may be removed by breaking the roof of the orbit with a 

 hammer, removing the fragments of bone, and dissecting away bone and 

 muscles, so as to expose the optic nerve and posterior segment of the 

 eye. That portion of the globe which is not covered by conjunctiva can 

 DOW be cut away with scissors and removed with the optic nerve, or, 

 when permissible, the whole eye may be cut out. 



The examination of the internal ear may be made by removing its 

 entire bony encasement with the saw and chisel, or by the exposure of 

 special parts by hammer and chisel, and by suitable opening of the re- 

 moved parts with a fine saw. 



HARDENING AND PRESERVATION OF THE TISSUES FOR MICROSCOPICAL EXAMINATION. 



For the study of tumors and inflammatory lesions of the bones of the skull and 

 ossifications of the dura mater and pia mater, the affected portions should be cut into 

 small pieces, fixed in five-per-cent. formalin or in Orth's fluid, see page 53, and decalci- 

 fied. The dura mater should be stretched on a flat piece of wood or cork with pins, 

 before hardening. ' 



The pia mater is so delicate that if it be separated from the brain when quite fresh 

 its tissues are apt to be injured. The portions of the pia mater which are to be pre- 

 served should therefore be removed by cutting off slices of the brain substance about 

 half an inch thick, with the membrane still attached, and placing the whole in Orth's 

 fluid. After twenty-four hours, the pia mater will have become sufficiently hard to 

 permit of its being stripped off without injury, and it is then spread loosely on a flat 

 cork with pins, the free surface outward, and the cork floated, specimen side down, in 

 eighty-per-cent alcohol, changing to strong alcohol after twenty-four hours. 



When sections are required showing the pia in its relationship to the underlying 

 brain tissue, small blocks of the brain and pia together should be cut out and hardened 

 in Orth's fluid or in formalin (5 : 100) solution (see page 53). 



When the ependyma is to be studied apart from the associated nerve tissue, it may 

 be sliced off with a sufficient quantity of underlying brain substance to prevent its fold- 

 ing, and hardened in Orth's fluid. The brain, for general purposes, may be hardened 

 in Orth's fluid or in five-per-cent formalin. The pieces of brain tissue should not be 

 more than 1 cm. thick ; it is better if they are thinner than this. They should be sus- 

 pended in gauze or rest upon a layer of absorbent cotton on the bottom of the jar, the 

 pieces, if these are numerous, being held apart by a little cotton. Thus the preserva- 

 tive fluid which should be abundant, is in contact with the surfaces of the pieces of 

 tissue. Ordinarily, with a change of fluid on the second day, the fixation by formalin 

 or Orth's fluid is complete in a week, when the fixatives are thoroughly washed out and 

 replaced by fifty-per-cent alcohol, which, in turn, is replaced after forty-eight hours by 

 eighty-per-cent or by ninty -five-per-cent alcohol. 



When degeneration in nerves is to be studied, the specimens of nerve tissue may, 

 by Marchi's method, be hardened for a week in M tiller's fluid, and then transferred to 

 the following solution: 



Mliller's fluid, . . . . . . .2 parts. 



Osmic acid, one per cent 1 part. 



After a week the specimens are washed and transferred to ninety-five-per-cer.t 



1 For details of the methods of hardening, decalcifying, staining, etc., see page 51. 



