12 THE HAllVEIAX ORATIOX, 1894. 



indicate contractile power in the vessels themselves. This 

 research was carried on under Ludwig's direction by various 

 of his scholars in succession, Alexander Schmidt, Dogiel, 

 Sadler, myself, Hafiz, Lepine, A. Mosso, von Fre}', and GaskelL 

 Their observations, as well as those of Colmheim and Gunning, 

 have shown that the muscular fibres of the arterioles, not only 

 in the muscles but throughout the body generally, have a power 

 of independent, and sometimes rhythmical, contraction and 

 relaxation. Their contractility is, however, controlled by the 

 central nervous system in accordance with the wants of the 

 body generally. For the amount of blood contained in the 

 body is insufficient to fill the whole of the vascular system at 

 once ; and when the vessels are fully dilated, as they are after 

 death, we find that nearly the whole of the blood of the body 

 may be contained in the veins alone. It is, therefore, neces- 

 sary that when one part of the body is receiving a larger supply 

 of blood, another should be receiving a smaller supply; and 

 the functions of the vaso-motor centres have been well com- 

 pared by Ludwig to the turncocks in a great city, who cut oft 

 the water supply from one district at the same time they turn 

 it on to another. Thus it is that when the brain is active the 

 feet may get cold, and Mosso has shown this in an exceedingly 

 neat manner by placing a man on a large board delicately 

 balanced at its centre, and demonstrating that whenever the 

 man begins to think, the increased supply of blood to his 

 brain causes the head to go down and the heels to rise up. A 

 similar condition was indicated by Mayow, who gave a different 

 explanation. He said that the " vital spirits " were not able to be 

 in more than one place at once, and therefore it happens that if 

 a man eats a heavy meal he is apt to become drowsy, because the 

 " vital spirits " descend from the brain to the stomach in order 

 to carry on digestion ; and, on the other hand, if a man thinks 

 vigorously after dinner, the " vital spirits " have to leave the 

 stomach to go to the brain, and consequently digestion is im- 

 perfectly performed. If we substitute the word blood for 

 " vital spirits," we have an exact expression of present physio- 

 logical ideas. 



