GENERAL CONDITIONS OF BRAIN-ACTIVITT. 99 



or emotional. He relates of his female subject that one 

 day whilst tracing her brain-pulse he observed a sudden 

 rise with no apparent outer or inner cause. She however 

 confessed to him afterwards that at that moment she had 

 caught sight of a skull on top of a piece of furniture in the 

 room, and that this had given her a slight emotion. 



The fluctuations of the blood supply to the brain were 

 independent of respiratory changes,* and followed the 

 quickening of mental activity almost immediately. We 

 must suppose a very delicate adjustment whereby the cir- 

 culation follows the needs of the cerebral activity. Blood 

 very likel}- may rush to each region of the cortex accord- 

 ing as it is most active, but of this we know nothing. I need 

 hardly say that the activity of the nervous matter is the 

 primary phenomenon, and the afflux of blood its secondary 

 consequence. Man}- popular writers talk as if it were 

 the other way about, and as if mental activity were due to 

 the afflux of blood. But, as Professor H. N. Martin has 

 well said, "that belief has no physiological foundation 

 whatever; it is even directly opposed to all that wc know of 

 cell life."t A chronic pathological congestion may, it is true, 

 have secondaiy consequences, but the primaiy congestions 

 which wc have been considering follow the activity of the 

 brain-cells by an adaptive reflex vaso-motor mechanism 

 doubtless as elaborate as that which harmonizes blood- 

 supply with cell-action in any muscle or gland. 



Of the changes in the cerebral circulation cku'ing sleep 

 I will speak in th(» chaptei' which treats of that subject. 



CEREBRAL THERMOMETRY. 



Brain-activity seems accompanied by a local disengagement 

 of heat. The earliest careful work in this direction was by 

 Dr. J, S. Lombard in 1867, Dr. Lombard's latest results in- 

 clude the records of over 60,000 observations.:}: He noted the 



■^ lu this conclusiou M. Gley (Archives de Pbysiologie, 1881, p. 743) 

 agrees with Professor Mosso. Gley found his pulse rise 1-3 beats, his 

 carotid dilate, and his radial artery contract during hard mental work. 

 f Address before Med. and Chirurg. Society of Maryland, 1879, 

 X See his book; " Experimental Researches on the Regional Tempera 

 ture of the Head" (London, 1879). 



