The diagnosis of nervous diseases.

  • Purves-Stewart, James, Sir.
Date:
1906
Catalogue details

Licence: In copyright

Credit: The diagnosis of nervous diseases. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    Most of the fibres for tactile sense, together with those for temperature and pain, cross in the anterior commissure to the opposite side (these crossed fibres not coming directly from the posterior root, but through the relay of another cell in the posterior horn) and ascend the cord in the opposite lateral column, in the spino-thalamic tract. Thus the lateral column conducts not only pyramidal motor impulses coming down, but also spino-thalamic ascending impulses of touch, temperature and pain. The upward course of the various sensory fibres through the medulla and pons is somewhat complicated, and not yet entirely settled, but the most probable arrangement is shown in Fig. 9. Most of the fibres for touch cross the middle line in the spinal cord, as already explained, and then pass directly upwards in the spino-thalamic tract of the lateral column and into that part of the medulla called the jormatio reticularis. The formatio reticularis leads the fibres up through the pons and crus to the optic thalamus, and thence they pass through the posterior limb of the internal capsule to the sensory cortex behind the fissure of Rolando. As the sensory tract traverses the pons it passes' along the inner side of the sensory spinal root of the trigeminal nerve of the same side. Thus a unilateral lesion of the formatio reticularis below the exit of the fifth or trigeminal nerve will produce a crossed ana3sthesia, i.e. anaesthesia of the face on the side of the lesion, and of the arm, leg, and trunk of the opposite side. But higher up the pons the sensory fibres from the face also cross the middle line, so that a lesion of the formatio reticularis in the crus cerebri will now cause complete hemiansesthesia of face, arm, and leg (see Fig. 10). The fibres for temperature and pain, entering like the others by the posterior root, pass into the grey matter of the posterior cornu. There they start afresh and cross to the opposite side of the cord, ascending in the opposite lateral column near the crossed tactile fibres. On reaching the medulla, they diverge from the tactile fibres and pass to the outer side of the olivary body, close to the lateral margin of the medulla and intermingled with the fibres of Gowers' tract. They then leave the region of Gowers'