990 THE CENTRAL NERVOUS SYSTEM 



frontal lobe is supplied by the anterior cerebral, and the occipital lobe, 

 with the lower part of the temporal lobe, by the posterior cerebral. 

 The medulla oblongata, cerebellum, and pons are fed from the verte- 

 brals and the basilar artery before the circle of Willis has been formed. 



Resuscitation of the Central Nervous System after Total Anaemia. 

 Complete temporary anaemia of the brain and upper cervical 

 cord can be produced in most cats by passing temporary ligatures 

 around the innominate artery and left subclavian proximal to 

 the origin of the vertebral artery. Artificial respiration is main- 

 tained through a tube passed through the glottis. The eye reflexes 

 disappear very quickly, and a period of high blood-pressure imme- 

 diately follows the occlusion. A fall of pressure succeeds, due to 

 vagus inhibition of the heart, and this is followed by a second rise 

 after the vagus centre succumbs to the anaemia. Respiration stops 

 temporarily (in twenty to sixty seconds) after occlusion; then 

 follows a series of strong gasps, and finally cessation of all respiratory 

 movements. The blood- pressure slowly falls to a level which is then 

 maintained approximately constant for the remainder of the occlu- 

 sion period. The anterior part of the cord and the encephalon lose 

 all function; no reflexes can be elicited from this part of the central 

 nervous system. The intra-ocular tension is much reduced, and the 

 cornea is characteristically wrinkled. 



When the cerebral circulation is restored by releasing the vessels, 

 the general arterial pressure soon begins to rise if the period of 

 occlusion has not overstepped the limit of successful cardio- vascular 

 resuscitation. The respiration returns suddenly, the time of 

 return depending on the length of the occlusion and on other factors. 

 The respiratory rate, at first slow, soon becomes normal, and then 

 more rapid than normal. The eye-reflexes reappear more gradu- 

 ally; the intra-ocular tension increases, and the shrunken cornea 

 becomes smooth and hard. The anterior part of the cord recovers 

 its functions gradually; the reflexes connected with it return, first 

 the homonymous, then the crossed. A short period of quiet follows ; 

 then spasms of the skeletal muscles appear, gradually increase in 

 severity and extent, and terminate in (a) death, (b) partial, or 

 (c) complete recovery. In partial recovery, disturbances of loco- 

 motion, such as walking in a circle, paralysis, apparent dementia 

 or loss of intelligence, and loss of sight or hearing, may be observed. 

 Voluntary movements of the head, neck, shoulders, and fore-limbs 

 have been seen eight minutes after release from an occlusion of six 

 minutes. Blindness has been observed without loss of the pupillary 

 light reflex. In this case the visual cortex would seem to have 

 suffered more than the lower centres, an illustration of a general 

 rule. Complete recovery is rare after total anaemia lasting as much 

 as fifteen minutes, and has not been observed after an anaemia of 

 twenty minutes. Ten to fifteen minutes of total anaemia represent 



