( 7S ) 



STEPHEN HALES. 



1677-1761. 



MEDICINE owes much to the sons of the Church. Stephen 

 Hales was not a medical man, nor had he the advantage 

 of a medical education. Born the son of a baronet, in 

 1677, at Bekesbourne, in Kent, he was educated at Cambridge, and 

 describes himself in his famous Statical Essays as Rector of Farringdon, 

 Hampshire, and Minister of Teddington, Middlesex. In the original 

 picture from which our collotype is taken, he is described as " Clark of 

 the Closet to her Royal Highness the Princess Dowager of Wales," 

 D.D., F.R.S. (set. 82). 



All through life he kept experimenting on a great variety of 

 subjects. The records are most carefully kept and every detail 

 entered. He worked chiefly at Teddington. He wrote an Essay 

 Against the Use of Spirits and was thus an advocate of temperance 

 principles and others on Freshening Sea Water, and Preserving Meat 

 during long sea voyages. He invented a " ventilator " for purifying the 

 air of ships, and thus became a pioneer in sanitary reform. He was 

 an F.R.S. , and the Royal Society published his Statical Essays. 



Volume one, which contains his Vegetable Staticks on the sap in 

 vegetables, also a Specimen of an Attempt to Analyse the Air by a 

 Great Variety of Chymico- Statical Experiments, was published 

 (1726-27). 



Volume two 1733 contains Hcemastatics. This deals with the 

 haemodynamics of the circulation. He was the first to determine, by 

 experiment on a living animal, the exact pressure of the blood on the 

 blood-vessels. Previously he had determined the pressure of the 

 ascent of the sap in the vine and many other interesting phenomena. 



"VEGETABLE STATICKS." EXPERIMENT XXXVII. 



" April 4th, I fixed three mercurial gages (Fig. 19) a, l>, c, to a vine, on a south-east 

 aspect, which was 50 feet long, from the root to the end ru. The top of the wall was 1 1 + J 

 feet high ; from i to k, 8 feet ; from k to e, 6 feet + | ; from e to a, 1 foot+ 10 inches ; 

 from e to o, 7 feet ; from o to 6, 5 + J feet ; from o to c, 22 feet 9 inches ; from o to u, 

 32 feet 9 inches. The branches to which a and c were fixed were thriving shoots two 

 years old, but the branch ob was much older. 



" When I first fixed them, the mercury was pushed by the force of the sap, in all the 

 gages down the legs 4, 5, 1 3, so as to rise nine inches higher in the other legs. 



" The next morning at 7 a.m. the mercury in a was pushed 14 + ^ inches high, in b 

 12 + ^, in c 13 + i. The greatest height to which they pushed the sap severally was, a 

 21 inches, b 26 inches, c 26 inches. The mercury constantly subsided by the retreat of 

 the sap about 9 or 10 in the morning, when the sun grew hot ; but in a very moist foggy 

 morning the sap was later before it retreated, viz., till noon, or some time after the fog 

 was gone. 



