Tributes 



analysing small samples of blood for their contents of gases, by 

 his introduction of the now familiar differential manometric method. 

 This, I suppose, with the modifications and elaborations of detail 

 which others have added to give it a more general application, may be 

 regarded as one of Barcroft's greatest gifts to experimental physiology 

 and biochemistry. In one form or another, with his own, or more 

 frequently Warburg's, name attached to it, it has become a part of 

 the standard equipment of almost any laboratory of experimental 

 biology. In Barcroft's own hands, and in those of a series of collab- 

 orators, it found its first use, however, in the next and, perhaps the most 

 important of the phases of his research activities, in which he dealt 

 with the oxygen dissociation curve of blood, and brought this for the 

 first time into clear and intelligible relationship with the dissociation 

 curve of free haemoglobin, by demonstrating the effects on the latter 

 of the presence of different salts and of carbon dioxide. Hitherto he 

 had been dealing with blood simply as a vehicle, and his attention had 

 been concentrated on the tissue activities and the consequent abstraction 

 of oxygen from and addition of carbon dioxide to the blood. Now he 

 turned to the factors controlling the behaviour of the vehicle itself and 

 favouring the uptake or outlet of oxygen by the blood. This study of 

 the dissociation curves of blood and of haemoglobin was doubtless to 

 play an important part in the development of Barcroft's interest in 

 physiology at high altitudes and, more generally, in the respiratory 

 functions of the blood itself. At that point, however, I feel sure that I 

 ought to stand down in favour of Krogh, Douglas, Hill and the others 

 who are to follow me. Before I do so, I should like to make just passing 

 mention of one of Barcroft's minor interests, growing out of his work 

 on the salivary gland. His attention was attracted by the functional 

 vasodilatation so conspicuously seen in that gland with stimulation of 

 the chorda tympani. In more than one publication he made a tentative 

 case for regarding all such vasodilator effects as due to the release of 

 rather vaguely described ' metabolites '. That of course was before 

 there was any precise knowledge of natural vasodilators such as 

 histamine, and long before there was talk of cholinergic nerves. 

 Although such more recent evidence has not supported Barcroft's idea 

 that substances released by the functional activity of a gland or other 

 organ may be the sole cause of the concomitant vasodilatation, I do not 

 think that such a secondary effect has yet been by any means excluded 

 as a possible contributory factor. 



I have not had time to do more than touch on some of the 

 main features of Barcroft's activities in his first period. Apart from 

 publications in the Journal of Physiology, which I have mentioned, 

 there is a great deal of personal observation by himself to be found 



