512 



Mr. W. Duddell. On the Resistance and 



red colouring matter containing both the albuminous and the iron-con- 

 taining residues of haemoglobin. In the case of CO-haemoglobin the 

 compound deposited has presented the peculiar colour of CO-haemo- 

 globin. 



General Conclusions. 



The following are the conclusions to which I have been led by my 

 experiments : — 



1. The blood-colouring matter, oxy-haemoglobin, as well as carbonic- 

 oxide haemoglobin and methaemoglobin, are decidedly diamagnetic 

 bodies. 



2. The iron-containing derivatives haematin and acethaemin are 

 powerfully magnetic bodies. The differences in magnetic behaviour 

 between the blood-colouring matter and acethaemin and haematin point 

 to the profound transformation which occurs in the haemoglobin 

 molecule when it is decomposed in the presence of oxygen. 



3. The preliminary study of the electrolysis of oxy-haemoglobin and 

 CO-haemoglobin renders it probable that, in the blood-colouring matter, 

 the iron-containing group, on which its physiological properties depend,, 

 is (or is contained in) an electro-negative radical : according to analogy, 

 the iron in such a compound would possess diamagnetic and not 

 magnetic properties. 



In conclusion, I beg to acknowledge my indebtedness to Professor 

 von Bunge, of Basel, to Professor Franz Hofmeister, of Strassburg, 

 and to Dr. v. Ehrenberg, the technical director of the chemical factory 

 of Messrs. Merck, of Darmstadt, for their great courtesy and kindness, 

 in placing at my disposal preparations of haemoglobin prepared by 

 themselves or under their direction. I have further to add that I 

 reserve to myself the right of continuing without delay the researches 

 of which the first results are contained in this paper. 



" On the Besistance and Electromotive Forces of the Electric- 

 Arc." By W. Duddell, Whitworth Scholar. Communicated 

 by Professor W. E. Ayrton, F.B.S. Beceived and Bead 

 June 20, 1901. 



(Abstract.) 



The discrimination between resistances and electromotive forces in 

 conductors, or apparatus, in which both of these quantities are functions 

 of the current is considered, and it is pointed out that whether such 

 an apparatus may be said to possess a resistance, or an E.M.F., or both, 

 depends to a large extent on the nature of the definition of these 

 quantities, and a definition of these quantities is adopted. 



