At autopsy the spine and dura mater proved normal; but microscopically serial sections through the fourth and fifth dorsal segments showed softening of the right anterior horn and posterior columns, with cavitation in the radicular zones, and the white matter of the fifth dorsal segment was in a state of acute degeneration. There were also ependymal changes, namely, at the fifth dorsal level a dilatation with deposit of albumin; in the lumbar region, breakage of the ependymal wall, with cellular gliosis. The dilated ependyma was surrounded by an area of fibrillary gliosis which had proliferated in the form of a septum in the interior of the canal. (According to Claude and Lhermitte, these data concerning hydromyelia, which they regard as secondary to trauma, are an argument in favor of the traumatic origin of certain syringomyelias. They regard the breakage of the ependymal wall as due to hypertension of the spinal fluid due to mechanical lesions.) Their interpretation of such acute degeneration as was found in the fifth segment is that this degeneration, as well as that of the posterior roots, is due to the direct impact of the cerebrospinal fluid upon the cord structure. As for the softenings with cavitation, they regard them as surely due to spinal concussion and as very possibly due to an ischemic necrosis, suggesting that older work by Duret and Michel on concussion of the brain indicates the possibility of a temporary ischemia of the spinal cord from the violent impact of the spinal fluid upon the cord due to shock of the spinal column. The transient hypertension of the spinal fluid might well induce, they believe, a vascular spasm with anemia, to which the gray matter is well known to be especially sensitive. In the present case, a period of somewhat less than six weeks had sufficed to produce secondary degenerations above and below the fifth dorsal segment, of a quite classical sort. Accordingly, we here deal with a severe form of spinal concussion due to a shellburst, in which intraspinal lesions were produced without spinal fracture or penetration either of bone or of shell fragments into the spinal cord or the spinal fluid. Shell explosion (1 meter distant) kills a soldier by bursting both lungs within the intact thoracic cage. =Case 201.= (SENCERT, January, 1915.)