1905.] Oil Blood Pressure in Man. 5 



By these considerations the lecturer was led to explain why the 

 blood in the body does not drop down into our feet and legs, and leave 

 the brain and other vital parts. Indeed, the blood has a strong 

 disposition thus to obey the action of gravitation, and one of the 

 events of approaching death is the falling of the blood into lower 

 parts of the body, deserting the heart and brain. Obviously this is 

 especially the case in upright animals, as in man chiefly, and in apes in 

 some measure. It is by the vigilance of the nervous governance that 

 the blood is held up, by the contraction of the abdominal vascular 

 fields ; and it is the failure of these mechanisms which appears as 

 shock, syncope, or collapse. The lecturer, assisted by demonstrations 

 by Dr. Dixon, illustrated these dispositions, citing especially the re- 

 searches of Prof. Leonard Hill on the distribution of the blood in 

 various positions of the body. He also referred to the bearing of 

 these principles on the researches of Prof. Waller and others on the 

 dangers of anesthetics. By some most interesting experiments by 

 Dr. Cushing he showed how enormously the arterial pressures may be 

 raised in case of danger of failure of supply of blood against gravity 

 when, as in apoplexy or a depressed fracture of the skull, the blood- 

 vessels, in the parts of the brain where all these mechanisms find 

 their centres, are compressed and thus more or less liable to be 

 emptied. 



In the last part of the lecture the lecturer apologised for occupy- 

 ing time with so much physiology, in which subject he is not an 

 investigator. But it was necessary to make manifest to his audience 

 how great is the importance of the integrity of the arteries themselves, 

 and of their nervous governance in function, an integrity which is a 

 matter of hfe and death ; for if the circulation fails in the nervous 

 centres or heart, Hfe must cease. Now the arteries are subject to 

 many injurious conditions, as of certain poisons and infections, or of 

 hard muscular labour ; there are also the unexplained deteriorations 

 of age. His personal investigations had been into the effects on the 

 arteries of gradual increases of blood pressure. Normally, arterial 

 pressures, as taken in the arm, rise somewhat from childhood to age 

 — say from 80-90 mm. Hg. to 140° or perhaps 150°. These upper 

 limits are not inconsistent with health at the age of three score, 

 though no doubt they signify some loss of mechanical efficiency. A 

 demonstration was given by Dr. Dixon of the difference in vascular 

 efficiency under muscular effort between a young and an elderly man. 

 Into the notable effect of certain poisons and infections on the arteries 

 he could not enter. Senile degenerations of the arteries are not essen- 

 tially allied to rise of blood pressure, though in such subjects, as in 

 others, high pressures may arise, and must be, of course, the more 

 dangerous. Still, senile arterial degeneration is compatible with very 

 long life, even if with diminution of function, as the vessels close or 

 silt up rather than burst. 



The lectm-er's own observations, now extended over many years, 



