INTRODUCTION. xli 



May not, therefore, Dr. Davies be considered as having re- 

 vived and established that correct knowledge of the distinct 

 characters of the three parts of the blood which was taught by 

 Hewson, Fordyce, and the Hunters ? Certain it is that there 

 was a general ignorance on the subject in England when 

 Davies wrote his Essay. Nor was the gloom in which the 

 truth had been hid for nearly a century dispelled by the fitful 

 lights of the able French physiologists before mentioned. Hence 

 the honour of displacing the current errors by accurate doctrines 

 fairly settled on experimental proofs would appear to belong, 

 as Dr. Davy observes, chiefly to our countrymen. 



Among these Mr. Hewson was unrivalled, and has perhaps 

 never been surpassed, for the skill with which he prosecuted 

 this right method of inquiry. His work on the ' Properties of 

 the Blood' is a model of experiments nicely devised, well 

 executed, and clearly told ; often original, ever instructive ; a 

 happy combination of precision and simplicity, and an admi- 

 rable reflection of the character of his mind. 



Nothing can be plainer than the proofs given by Hewson 

 that the coagulation of the blood is alone dependent on the 

 fibrin ; nor is there a jot of evidence that either he or Davies 

 ever supposed that the red corpuscles have anything whatever 

 to do with that coagulation. On the contrary, Hewson was wont 

 to obtain them in the entire state from the clot ; he had well 

 established that their form in the blood is preserved by the 

 saline matter of the serum, and by watery solutions of neutral 

 salts out of the body ; while the mixture of these salts with the 

 blood was one of the means by which he separated the fibrin, 

 as Miiller afterwards did, from the red corpuscles. 



There was, indeed, an old and discarded hypothesis, already 

 noticed, entertained by Sydenham, Quesnay, and Bordenave, that 

 the fibrin of the blood is formed of the colourless matter of the 

 red corpuscles. Sir Everard Home 1 and Mr. Bauer revived this 

 opinion in the more specious form, that the fibres of fibrin and 

 of muscle are composed of rows of the nuclei of the corpuscles di- 

 vested of their coloured envelopes. A similar doctrine was soon 

 afterwards brought forward in France by Prevost and Dumas, 2 



1 Croonian Lectures, Philosophical Transactions, 1818 and 1820. 



2 Examen du Sang, Annales de Chimie et de Physique, torn, xviii et xxiii, 8vo, Paris, 

 1821 and 1823. 



d 



