7 i8 



PEDUNCLE AND PONS. 



unknown It is evident that hemorrhage into or about the basal ganglia is apt 

 to involve the fibres of the internal capsule. [When the lenticulo-stnate artery, 

 or as it is called the "artery of haemorrhage," ruptures (tig. 490, aSL), it may not 

 only destoy the lenticular nucleus, but the internal capsule will be compressed ; 

 and the same is the case with the lenticulo-optic artery the external capsule will 

 tend to force the blood inwards. We know that, in the posterior segment of the 

 capsule, the volitional or pyramidal fibres lie in the following order from before 

 backwards those for the face (and tongue) in the knee, in the anterior third 

 those for the arm and hand, and in the middle third for the leg, and perhaps behind 

 these those for the trunk (fig. 500, F, A, L), so that a very small lesion in this 

 region will affect a large number of these fibres, converging as they do like the 

 rays of a fan from the motor cortical areas, where the arrangement of these centres 

 is a supero-inferior one (fig. 488), to become an anteroposterior one in the knee 



and posterior limb of the 

 internal capsule (fig. 500). 

 The posterior third of this 

 limb is sensory and is the 



Nucleus 

 lauilatuv 



Corpus 

 callosum. 



Hilars of 

 the fornix 



Interna) 

 capsule. 



optic 

 thalamus. 



Soft com- 

 missure. 



Kxternal 

 capsule. 



Claustrum. 



sensory crossway. 



[Horsley points out that hae- 

 morrhage from the lenticulo- 

 striate artery affects in order the 

 muscles of the face, arm, leg, and 

 trunk, while recovery is in the 

 inverse order.] 



[The crura cerebri (fig. 

 461, P), or cerebral pe- 

 duncles, are two thick 

 strands as they emerge 

 above the pons, and as they 

 are much larger than the 

 pyramidal tracts, they must 

 receive many fibres within 

 the pons. A transverse sec- 

 tion (fig. 502) shows that, 

 on them posteriorly and con- 

 necting them, are the cor- 

 pora quadrigemina (CQ). 



. The cms proper is divided 

 Frontal section through the right cerebral hemisphere in front , .. i fl ftV fl /vr\ 



of the soft commissure (posterior surface of the section). b y the substantia nigra (bN) 



into a lower part, the crusta 

 or basis, and an upper part, or tegmentum. The crusta is composed of ascending 

 and descending nerve-fibres ; but the tegmentum, in addition to many nerve-fibres, 

 contains much grey matter with nerve-cells. Near the middle is the " red nucleus " 

 or " tegmental nucleus " (RN). Outside this is the fillet (F), a well-defined bundle 

 of nerve-fibres running upwards from the pons. Above the nucleus, near the middle 

 line, is the "posterior longitudinal bundle " (p. 1. b.), which is triangular in section. 

 Above the tegmentum lie many nerve-cells, the origin of the third nerve (III), and 

 arranged around the iter is much grey matter.] 



Injury to one cerebral peduncle causes, in the first place, violent pain and spasm 

 of the opposite side, while the blood-vessels on that side contract, and the salivary 

 glands secrete. These phenomena of irritation are followed by paralytic symptoms 

 of the opposite side, viz., anaesthesia ( 365) and paresis, or incomplete voluntary 

 control over the muscles, as well as paralysis of the vaso-motor nerves. In 

 affections of the cerebral peduncle in man, we must remember the relation of 





