THE TEGMENTUM AND THE PEDUNCLE OF THE MIDBRAIN. 309 



(&) The fibers which lie on the median side of the pyramis originate in the 

 lobus frontalis, those which lie outside of it, in the lobus parietalis et tem- 

 poralis, (c) A bundle leaves the pyramid at this point and, skirting the 

 border of the pes, joins the fillet farther back, forming the median layer 

 of that structure. Spitzka makes it probable, on comparative anatomical 

 grounds, that this bundle contains the cerebral tracts of the cranial nerves. 

 (d) Internal to it are visible the root-fibers of the motor-oculi nerve, (e) Just 

 before their emergence they traverse the pedunculus corporis mamillaris. 



The course of the fibers in the thalamic and subthalamic region is less thor- 

 oughly known than in most other regions of the brain. In this obscure field, Meynert, 

 Forel, Gudden, Flechsig, Ganser, Wernicke, Monakow, Kolliker, the author, and 

 others have worked. 



The origin of the optic nerve has been investigated by Meynert, J. Stilling, 

 Tartuferi, Gudden, Bellonci, and by Monakow (to whom we are indebted for most 

 important progress), by Henschen, et al. The motor-oculi nucleus is better known 

 since the labors of Gudden, Perlia, Westphal-Siemerling, Bernheimer, Kolliker, and 

 the author. 



It is of considerable importance to know what to regard as fairly accurate 

 signs of disease of the quadrigeminal region. Disease-foci in the regio subthalamica 

 encounter such a, tangle of various fibers that the resultant symptoms show great 

 diversity. A positive diagnosis could scarcely be possible. 



Lesions in the cerebral peduncle intercept the motor fibers to the opposite 

 half of the body and head. There may be added sensory and vasomotor disturbances. 

 Usually, however, not only paralysis of the opposite extremities and of one or several 

 cranial nerves results, but also weakness of the motor-oculi of the same side. When 

 simultaneous paralysis of one oeulo-motorius and of the opposite half of the body 

 exists, one may suspect a lesion belo«- the corpora quadrigemina. Such patients move 

 the limbs of one side feebly or not at all, %\ bile on the opposite side there are ptosis, 

 dilatation of the pupil, and abduction of the eyeball. A basal tumor may produce 

 the same symptoms {Cf. Fig. 237); it is, therefore, diagriostically important, when 

 paralysis of the ocular muscles and that of the extremities appear together, which 

 could only arise (as in the last-mentioned ease) through a peculiar combination of 

 circumstances. When anaesthesia is present, it is likewise confined to the opposite 

 side of the body. The sensory fibers probably course in the fillet. 



If the disease-focus extends farther dorsally, reaching the corpora quadrigemina 

 themselves, there ensues naturally, besides the unilateral or bilateral oculo-motor 

 paralysis of disease of the anterior quadrigeminal bodies, also visual disturbance; 

 occasionally nothing abnormal can be found ophthalmoscopically. With tumors 

 here, as elsewhere in the brain, there may follow choked disk, optie atrophy, etc. 

 Usually pupillary reaction is lost. 



The symptoms of disease of the posterior quadrigeminal bodies are not known. 

 Disturbances of equilibrium and co-ordination have accompanied it. 



Disease of the quadrigeminal region may be suspected when paralysis of both 

 motor oculi is present without peripheral {i.e., basal) cause, or when only a portion 

 of one motor oculi is injured (e.g., only the fibers to the internal rectus). Lesions 

 of the peripheral trunk could scarcely produce this, such paralysis being nearly 

 always nuclear in its origin. 



