. Diseases of the nervous system . eg-ment. At the same timeit becomes evident, as Ed-inger explains, that theotherwise obscure distribu-tion of cutaneous innerva-tion in the extremitiesdoes not actually repre-sent the case, because thediagram is based on em-bryology (Figs. 150 and151). However, we mayalso utilize the diagramsof other authors. For thesake of the findings Ihave included those ofSeiffer, as well as thoseof Head; the diagram ofthe latter author has en-abled me exactly to localizemany spinal cord tumors—at least their upper boun-daries (Figs. 152, 153,154,155, and 156). By the aid
. Diseases of the nervous system . eg-ment. At the same timeit becomes evident, as Ed-inger explains, that theotherwise obscure distribu-tion of cutaneous innerva-tion in the extremitiesdoes not actually repre-sent the case, because thediagram is based on em-bryology (Figs. 150 and151). However, we mayalso utilize the diagramsof other authors. For thesake of the findings Ihave included those ofSeiffer, as well as thoseof Head; the diagram ofthe latter author has en-abled me exactly to localizemany spinal cord tumors—at least their upper boun-daries (Figs. 152, 153,154,155, and 156). By the aid of thesediagrams we can usuallyascertain exactly the upperboundaries of a is only necessary tobear in mind the relationof the individual spinalcord segments to the ver-tebral bodies and thespinous processes belong-ing thereto. For this pur-pose Gowers table is valu-able; for it shows that thecauda equina begins op-posite the first lumbarvertebral bodies and theirFig. 155.—Diagram. (After Head.) spinous processes, and. THE SEAT, EXTENSION AND COMPOSITION 359 that the greater portion of the lumbar vertebral column does not lie oppositethe lumbar portion of the spinal cord (Fig. 158). After determining by the aid of these diagrams the upper boundary of atumor, we must ascertainits longitudinal extent andits lower boundary. Thisis often impossible, becausethe local phenomena due toabsence of function whichappear at the upper limitgenerally overshadow thoseproduced by pressure ofthe tumor upon the totaltransverse section of thespinal cord. It is easierto ascertain the longitu-dinal extension of the tu-mor within the cervicalenlargement, for when themuscles of the lower cer-vical segments remain un-involved there is no strongpressure upon these. Whenthe tumor is located op-posite the lower portion ofthe dorsal cord, and whenthe muscles belonging toit continue to show nodegenerative atrophy norDeR, we may concludethat it does not press uponthe upper portion of thelumbar
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