9o6 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOG^• II 



FIG. 14. Reflex sitting up in mesencephalic child. After pres- 

 sure on the legs, the anencephalus without cortex and basal 

 ganglia rises to a sitting position. Only the extrapyramidal 

 structures below the diencephalon were preserved; the red 

 nucleus, cerebellum and central tegmental tract were intact. 

 [From Gamper (66).] 



far better off in motor performance than otiier anen- 

 cephalic children ha\ing more of the basal ganglia 

 preserved and reaching a greater age. This contrast 

 arises because the pallidum is the main structure for 

 inducing rigidity in Parkinsonism. In all these 

 anencephalics there was atrophy of the substantia 

 nigra. Those with the pallidum intact showed rigidity 

 preventing normal postural reactions, but Camper's 

 child had no pallidum and therefore less rigidity. 



Another 'mesorhombencephalospinar anenceph- 

 alus having neither basal ganglia nor cerebellum was 

 studied by Monnier & Willi (194, 195) to the age 

 of 2 months and was compared with a rhomben- 

 cephalic bulbospinal anencephalus. As one might 

 expect from the lack of cerebellum and red nucleus, 

 it showed less motor ability than Camper's case but 

 more than the rhombencephalic one. Some mimic 

 expressions of aversion after pain and well-being 

 after satiation and warmth were preserved in the 

 mesencephalic case. This creature generally assumed 

 a sleeping attitude without spontaneous alteration of 

 sleep and wakefulness, but showed arousal after 

 sensory stimulation. Four pontobulbar anencephali 

 ("rhombencephalic beings') observed by Monnier & 

 Willi (193-195) lived onI\- i to 3 dass. All had dis- 

 turbances of respiration which was irregular, snapping 

 or periodic. Spontaneous motility was absent but 

 reflex movements could be elicited : spinal reflexes, 

 Moro's reflex and grasping refle.xes were present. 

 Oral feeding activity could be evoked by tactile 

 stimulation of the mouth and cheeks. The sucking 

 reflex was well developed in only one of these cases. 

 Tonic neck reflexes were absent, the righting refle.xes 

 doubtful. There was no decerebrate extensor rigidity 

 but increased flexor tone of the limbs appeared in all 

 four cases. Histological studies of the brain showed 

 the pontine structures partly developed in one, but 

 onlv bulbar structures in the other three cases. 



thine reflexes, the righting reflexes were also preserved 

 and Moro's reflex was intact. This creature resembled 

 mesencephalic animals according to Magnus' own 

 opinion. 



Camper's child had no decerebrate rigidity in con- 

 trast to t'he children without cortex described by 

 Edinger & Fischer (53) and by Jakob (129) in whom 

 the pallidum remained intact and who showed a 

 marked rigidity and akinesis resembling decerebrate 

 animals. Camper's child had reduced motor per- 

 formance but would assume a sitting position when 

 both lower legs were pressed (fig. 14). This child, 

 using only his midbrain, pons and cerebellum, was 



DECEREBR.ATioN PHENOMENA. The mcchanism of 

 decerebrate rigidity primarily involves the lower 

 brain-stem centers and therefore does not concern us 

 here. But it is to be rernembered that the main condi- 

 tion for exhibition of decerebration phenomena is an 

 elimination of the higher regulation of posture by 

 diencephalic and midbrain structures (including the 

 Slellreflexe of Magnus, Rademaker and co-workers, 

 and the Richtungsbeslimmte Bewegungsejfekle of Hess). 

 Rademaker's claim of a prominent role of the red 

 nucleus for Stellrejlexe and the appearance of decere- 

 iirate rigidity after red nucleus destruction was not 

 confirmed bv Mussen and others, using more selec- 



