216 



LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



The muscular atrophy which follows affections of the nuclei themselves 

 (see Fig. 68 and accompanying text) must be studied with scrupulous care if we 

 are to succeed in discovering the location and extent of such a disease. Fig. 132, 

 which gives you a general view of the nuclei in a longitudinal section through 

 the oblongata, will make this task somewhat easier for you than it was possible for 

 the transverse .sections through the nuclei to do. 



Disturbances of speech, respiration, or deglutition probably depend on 

 disease of the oblongata, paralysis of muscles of mastication (motor portion of 

 trigemirius), facial paralysis, or affections of the abducens on disease of the pons. 

 Inasmuch, however, as the central fibres to the nerve-nuclei of the oblongata 

 pass through the pons, a disease situated there may also cause disturbances of 

 deglutition. 



The motor tracts to the extremities lie anteriorly near the ventral border in 

 the pyramids. They only cross to the opposite side far down near the beginning 

 of the spinal cord. The motor fibres of the cranial nerves, on the other hand, lie 



FIG. 129. 



FIG. 130. 



FIG. 131. 



Three sections through the pons and quadrigeminal region of newborn children, 

 to show the course of the cerebellar peduncles and the layer of the fillet. The latter is 

 situated just above the fibres of the pons. The cerebellar peduncles, B (Fig. 129), are 

 situated more internally in Fig. 130, and are beginning the decussation, which is at its 

 height in Fig. 131. (Haeinatoxylin stain.) 



near the middle line. They ascend in the raphe of the tegmentum, and only cross 

 to the opposite side just before reaching the nucleus to which they are tending. 

 A disease in the pons, therefore, will generally involve the opposite extremities, 

 but will affect the facial abducens or trigeminns of its own side. The diagram 

 (Fig. 133) is intended to impress upon your memory more forcibly than can be done 

 by written descriptions this crossed paralysis, which is the most important symp- 

 tom in many affections of the pons and medulla. It represents the motor inner- 

 vatiou-tract for the face and extremities. You see from the cut that a lesion at A, 

 in the right side of the cerebrum or right crus, would paralyze the left facial nerve 

 and the left extremities. A disease at B, on the right, in the vicinity of the pons, 

 would still paralyze the left extremities but the right facial. Should such a disease 

 extend, beyond the middle line it might paralyze both facial nerves and the extremi- 

 ties on one side. You see, also, in the diagram, that a disease in the pons (at (7) 

 might be so situated as to give rise to unilateral, not alternating, hemiplegia, that 

 is, it may cause the same symptoms as though it were situated in the cerebrum. 

 Alternating paralysis can only (except in cases of multiple foci) be caused by dis- 



