126 THE GASES OF THE BLOOD. [BOOK I. 



SECT. 6. THE GASES OF THE BLOOD AS A WHOLE. 



Under the head of 'The Gases of the Liquor Sanguinis' and 'The 

 Gaseous Constituents of the Coloured Corpuscles,' it has been shewn 

 that from each of these constituent parts of the blood, there can be 

 separated, by certain methods of treatment, gases, which are a mixture 

 of carbonic acid, oxygen and nitrogen. We shall give a description 

 of the methods employed in separating the gases of the blood in 

 Chapter IV., and postpone a lengthened theoretical treatment of the 

 gases of the blood to the chapter on Respiration. In this place it will 

 suffice if we make the following brief statements. 



(1) The blood, when admitted into an empty space- and exposed to 

 the temperature of the body, readily gives up more than half its volume 

 of mixed gases, consisting of oxygen, carbon dioxide, and nitrogen. 



(2) The first (oxygen) is present in much larger quantities than 

 could be held in simple solution by the water of the blood, and, as will 

 be afterwards proved, is mainly held in feeble combination by the 

 haemoglobin of the coloured blood corpuscles; only a trace of it is, 

 under ordinary circumstances, held in solution in the liquor sanguinis. 



(3) The second (carbon dioxide), whilst not existing in larger 

 quantity in blood than it could do if simply dissolved by the water of 

 that fluid, is partly in a state of chemical combination but chiefly in 

 a state of simple solution. It is contained in great part in the liquor 

 sanguinis and serum, but in part also in the corpuscles. 



(4) The nitrogen is held in a state of simple solution in the liquor 

 sanguinis. 



(5) Arterial blood of the dog of mean composition yields for 

 every 100 volumes, 58'3 volumes of mixed gases (measured at C. 

 and 760 mm.), composed of 22 - 2 volumes of O, 34'3 volumes of 

 C0 2 , and 1*8 volumes of N, the maximum amount of oxygen observed 

 having been 25*4 volumes (Pfluger 1 ). 



(6) As venous blood differs in composition according to the 

 vascular area whence it is obtained, it is impossible to state the mean 

 composition of its gases ; the following facts are however correct : 

 the nitrogen is present in the same proportion as in arterial blood, 

 the is less in amount (from 8 to 12 volumes per 100 of blood) and 

 the C0 2 greater (from 40 50 volumes per 100 of blood). 



Summary of the .Quantitative Composition of the Blood. 



Having treated at length the properties of the individual constituents 

 of the blood, we shall here append tables exhibiting the results of 

 the elaborate researches of C. Schmidt and Lehmanu on the blood of man, 

 although some of the data have already been referred to in the preceding 

 pages. 



1 Efliiger, "Die normalen Gasmengen des arteriellen Blutes nach verbesserten 

 Methoden." Centralblatt f. d. med. Wissenschaft, 1868. 



