PART T 



THE CHEMISTRY OF HAEMOGLOBIN 

 CHAPTER I 



THE SPECIFIC OXYGEN CAPACITY OF BLOOD 



WRITERS on historical subjects frequently allow themselves to 

 speculate upon the momentous issues which follow from trivial 

 circumstances. A general stays to drink the health of his king in 

 some tavern, and the delay determines the result of a battle and 

 therewith also the reigning dynasty and thgJatutc religion. In like 

 manner I have sometimes indulged in the luxury of inquiring what 

 would have happened to the animal kingdom had it not been for 

 the accidental occurrence of the chemical substance haemoglobin. 

 Consider the respiration of muscle. It is among the most efficient of 

 machines. In warm-blooded animals muscle when working at its full 

 power uses up its own volume of oxygen in about ten minutes' 1 '. This 

 oxygen is carried to it by the haemoglobin of the blood a substance 

 so rich in oxygen that a relatively small quantity of blood satisfies 

 the need of the muscle. Were it not for this red pigment some 200 c.c. 

 of fluid would have to be circulated through every gram of muscle in 

 ten minutes of time. 



To put the matter in another way ; blood carries about 40 times 

 as much oxygen as the same volume of plasma. Therefore to convey 

 as much oxygen round the body as is carried by the blood, would in 

 the absence of haemoglobin demand 150 kilos of plasma, or perhaps 

 more. The contents of the vascular system would therefore amount 

 to twice the present weight of the body. The body would in short 

 be unable to cope with the weight of its own blood. The whole basis 

 of its economy therefore hinges upon the accidental possibility of the 

 occurrence and properties of haemoglobin. 



Nor is there any chemical substance which exactly resembles 

 haemoglobin, though in some of the lower animals there are poor 

 imitations of it. But for its existence man might never have at- 

 tained any activity which the lobster does not possess, or had he 

 done so, it would have been with a body as minute as the fly's. 



B. K. F. 1 



