180 OF THE BLOOD. 



mal proportions of the constituents of its blood. The analyses of the blood 

 drawn from the aorta in six healthy individuals yielded the following results : 



Mean. Max. Min. 



Fibrin . -'^ : '-; ;: '. . . 1.65 2.00 1.45 



Corpuscles 82.35 92.00 70.00 



Albumen .:,,: ;i. '/.:,: r . 46.30 58.00 37.20 



On the other hand, the analyses of the blood of three individuals which had 

 been made to respire pure oxygen for half an hour, gave the following as the 

 proportions of its components : 



Mean. Max. Min. 



Fibrin 2.40 2.50 2.30 



Corpuscles 69.56 75.00 60.50 



Albumen 40.23 45.70 35.00 



It is further stated by Dr. G-airdner (Op. cit., p. 183), that a rabbit having 

 been kept for half an hour under the influence of an electro-magnetic current 

 between the chest and spine, which produced a great acceleration in the respi- 

 ratory movements, its blood was found to contain as much as 2.9 parts of fibrin 

 in 10"00. The larger quantity of fibrin in arterial blood of itself renders its 

 coagulum firmer; but independently of this, there would seem to be a difference 

 in the quality of the fibrin, which, when separated by stirring or whipping, is 

 more tenacious and compact in arterial than in venous blood. 



165. The proportion of Red Corpuscles in arterial and venous blood respect- 

 ively, has been variously stated by different observers; and we may easily con- 

 ceive it to be affected by several circumstances, which may produce a change in 

 the whole proportion of the solid to the fluid constituents of the blood, during 

 the course of its circulation. Thus, the discharge of the contents of the thora- 

 cic duct into the venous system near the heart, will tend to dilute the blood of 

 the pulmonary and arterial circulation; whilst, conversely, the escape of the 

 watery part of the blood by the renal and cutaneous secretions, and by trans- 

 udation into the tissues, which takes place during its passage through the sys- 

 temic capillaries, will tend to augment the proportion of the solids of the blood 

 drawn from the systemic veins. On the other hand, if the discharge of fluid 

 from the thoracic duct be suspended, and the amount absorbed from the tissues 

 during the systemic circulation should exceed that which is transuded (as ap- 

 pears sometimes to happen, 162), then the proportion of solid matter will be 

 ' less in venous than in arterial blood. No such explanation will apply, however, 

 to the very marked differences exhibited in Dr. Gairdner's experiments just 

 cited, between the proportions of red corpuscles and of albumen in the ordinary 

 arterial blood of rabbits, and in that of the individuals whose blood had been 

 hyper-arterialized; the sum of the averages in the former case being 128.65, 

 and in the latter 109.79, the difference of which is 18.86, or nearly one-seventh 

 of the larger amount. Still, that this difference is in great part due, rather to 

 dilution of the blood than to the absolute diminution in its entire amount of 

 red corpuscles and of albumen, would seem probable from the fact that their 

 relative amount is almost exactly the same in the two cases, the proportion of 

 corpuscles to albumen being 1.78 : 1 in the normal blood, and 1.72 : 1 in the 

 oxygenated. 1 



166. The difference in the hues of arterial and of venous blood, which is 

 entirely dependent upon the state of the Red Corpuscles, has been supposed to 

 be produced by a chemical change exerted upon their Haematin ( 31) by oxygen 



1 It would be important to determine the comparative amount of carbonic acid, and of 

 the solids of the urine, excreted in the same time by two sets of animals placed under 

 these very diverse conditions. 



