xxxviii INTRODUCTION. 



out of its vessels, whether in motion or at rest, exposed to the 

 air or not, in the heat of the human body or in any other de- 

 gree of heat ; continuing fluid for more than three hours when 

 retained in the blood-vessels, in motion or at rest, in any heat 

 between 30 and 120 ; and its coagulation prevented by satu- 

 rating the whole blood with common salt and perhaps by some 

 of the other neutral salts. His account of the formation of the 

 buify coat is similar to Hewson' s, even stating that it will occur 

 on blood which has some time been stagnated in its vessels 

 before it is let out. Dr. Fordyce had a perfectly clear know- 

 ledge of the distinction between the coagulable lymph, the red 

 corpuscles, and the serum. Fordyce and Houlston are probably 

 alluded to in Hewson' s note to the end of the second chapter 

 of the first part of his ' Experimental Inquiries/ p. 41, where he 

 says that his facts had been mentioned in his lectures ever since 

 1767 or before. A creditable contemporary writer, Dr. David 

 Macbride 1 first quotes Fordyce concerning the buffy coat, but 

 afterwards 2 corrected himself by adding that " the late Mr. 

 Hewson was the first that accounted for the formation of the 

 buff in the manner above described :" and Dr. Foart Simmons, 3 

 after having quoted the same observation on the authority of 

 Dr. Fordyce, concluded by giving it entirely to Mr. Hewson. 

 In the library of the medical department of the army, at 

 Chatham, there is a quarto copy of manuscript notes from Dr. 

 Fordyce's Lectures on the Practice of Physic, marked on the 

 cover, " E. Scott, 1 764." The term coagulable lymph is cor- 

 rectly used in that manuscript for a part of the matter which 

 causes the swelling in inflammation, and incorrectly for the 

 lateritious sediment of the urine in the same disease. 



Hewson removed the coagulable lymph in its fluid state from 

 the blood, and proved that the coagulation of the lymph is 

 quite independent of the other parts. His experiments on 

 the effects of various temperatures on its coagulation are very 

 interesting and original; by freezing the blood he suspended 

 its coagulating power, and restored it by thawing. To enable 



1 A Methodical Introduction to the Theory and Practice of Physic, pp. 229-30, 

 4to, London, 1772. 



2 Op. cit. 2d edit. vol. i, p. 294, 8vo, Dublin, 1777. 



3 Elements of Anatomy, from the French of M. Person, note to p. 327, 8vo, Lond. 

 1775 ; and 2d edit. 1781, p. 345. 



