142 



THE MECHANISM OF THE CIRCULATION. 



the greatest ease, by applying a sensitive recording tambour to the 

 fontanel of a newborn child. 1 



Galen and his followers thought that by the diastole of the brain, 

 the ffvevfia, the spirit of life, was sucked in through the cribriform plate, 

 and mingled with the vital spirit, which ascended by the arteries from 

 the heart. It was supposed that the dura mater pulsated, and by 

 driving onward the animal spirits, produced movements of the muscles, 

 and stimulated the soul. De la Mure, Haller, 2 and Lorry, 8 in the 

 eighteenth century, by finally establishing the cardiac and respiratory 



Fig. 87. — Respiration (A) and cerebral pulse tracing. Downstroke = inspiration. — Mosso. 



origin of the cerebral pulsation, proved that the dura possessed no inde- 

 pendent power of movement in itself. They showed that the collapse 

 of the chest wall pressed upon the thoracic veins, and drove back the 

 venous blood, thus causing the expiratory expansion of the brain. 



The movements of the brain in the closed cranium can be demonstrated in 

 the following way : — 



The skull is trephined, the trephine hole wormed with a mechanic's tap, 



the dura mater carefully 

 . divided without causing 

 any haemorrhage, and a 

 piece of steel tubing (B) 

 screwed into the hole. 

 Over the end of a piece 

 of brass tubing (A), of 

 smaller diameter than 

 the steel tube, a piece 

 of thin indiarubber 



amj WW i—^^-- 



•Cerebral pressure gauge. — Hill 

 This second tube is passed into the steel tube, and the two 



Fig. 88.- 



membrane is tied 



are screwed together by means of a male and female screw. 4 By means of this 

 mechanism the indiarubber membrane comes into exact apposition with the 

 brain. Attached to the end of the brass tubing is a piece of glass tubing of a 

 fine bore. This is connected with a T-piece, one branch of which leads to a 

 pressure bottle, and another to a mercury manometer. The whole apparatus 

 is completely filled with water, and a bubble of air, to act as an index, is 

 introduced within the fine- bored glass tubing. Before the apparatus is screwed 

 in, the normal no-pressure position of the air index, when the tube is held 



1 Leyden, Virchoio's Arehiv, 1866, Bd. xxxvii. S. 519; Salathe, "Trav. du labor, de 

 Marey," 1876, tome ii. p. 345 ; Mosso, " Ueber den Kreislauf des Blutes im mensehlichen 

 Gehirn," Leipzig, 1881. 



2 Haller, "Elem. Physiol.," lib. x. vol. vii. p. 301. 



3 Lorry, Mim. de math, etphya. Acad. roi/. d. sc., Paris, 1760, vol. iii. p. 277. 



4 Hill, "Cerebral Circulation'," p. 9. 



