THE METHOD OF MAKING POST-MORTEM EXAMINATIONS. 19 



pigmentations. Important lesions of the cord may be invisible to the 

 naked eye, and hence, if disease be suspected, the organ should be pre- 

 served for microscopical examination. The spinal ganglia may now be 

 removed and preserved for further examination. After removal of the 

 cord, fractures and displacements of the vertebra are easily recognized. 



PRESERVATION OF THE SPINAL CORD AND ITS MEMBRANES, AND OF PERIPHERAL 

 NERVES. After the removal of the spinal dura, the entire cord with its nerve roots 

 the segments into which it has been cut for gross examination being left in place should 

 be laid on a wad of absorbent cotton in a large jar of Orth's fluid or formalin, the seg- 

 ments being slightly separated from each other by a little absorbent cotton. Van Gie- 

 son recommends the careful rolling of the segmented cord into a loose spiral and laying 

 this coil on a wad of absorbent cotton in the fixative. In this way the cut ends of the 

 segments are held apart, accessible to the fluid, and harden with little distortion. 



The hardening and preservation of the cord may be done by the same methods as 

 suggested above for the brain. If the dura mater of the cord alone is to be preserved, 

 it should be treated in the manner suggested for the dura mater cerebralis. The pia 

 mater spinalis is best studied in sections through the entire cord, the membranes being 

 left in situ. 



Peripheral nerves may be hardened in Orth's fluid or in formalin. 



For the hardening of the peripheral nerves, osmic acid is very useful, especially 

 when changes in the myelin are to be sought after. As osmic acid does not readily 

 penetrate the lamellar sheath so as to come in contact with the nerve fibres, in trunks 

 of any considerable size, the following procedure, as suggested by Van Gieson, will be 

 found useful : A piece about one-half inch long is cut from the nerve to be examined : 

 one end of this segment is held with a forceps, while with another forceps the individual 

 nerve fibres, or small clusters of these, are pulled out of the lamellar sheath and put at 

 once in a one-per-cent aqueous solution of osmic acid, in which they remain twenty-four 

 hours, and are then washed and transferred to glycerin, to which twenty -five per cent 

 alcohol is added. In this mixture they may be preserved. Marchi's method (see above, 

 p. 16) is useful for the study of degeneration in peripheral nerves. 



THE THORAX AND ABDOMEN. 



The body is replaced on its back, and a single straight incision is 

 made from the top of the sternum to the pubes, passing to the left of the 

 umbilicus. For this purpose a large knife should be used, held firmly 

 in the whole hand, and the movement should be mainly from the shoul- 

 der. The first incision should divide everything down to the sternum 

 and peritoneum. A short incision should then be made through the 

 peritoneum, just below the ensiform cartilage. Into this opening two 

 fingers of the left hand are introduced and separated from one another, 

 and, the parietes being raised and the sides of the opening being held 

 apart by the fingers, the peritoneum is divided to the pubes, care being 

 taken to hold the knife horizontally so as not to cut the intestines. The 

 skin and muscles are then dissected off from the thorax on both sides as 

 far back as the false ribs. 



This dissection should be made by long sweeps of the knife, which 

 should be made to cut with the full blade and not with the point only : 

 and if the skin and muscles be pulled strongly away from the chest with 

 the left hand, it may be done very rapidly and with a few strokes of the 

 knife. We notice here the amount of subcutaneous fat and the coudi- 



