BLOOD. 153 



velopment of certain substances in the blood, produced by a 

 certain ^'ital power inherent in this fluid, with the aid of neces- 

 sary potential forces, as, for instance, of oxygen. This change 

 or metamorphosis represents the real vitality of the blood, and, 

 as far as we at present understand it, we may describe it as a 

 process in which not only blood-corpuscles are formed, (by a 

 consumption of lymph-, chyle-, and fat-globules,) and fibrin is 

 produced, but further, in which the blood-corpuscles are again 

 consumed ; for it is obvious that if there is a continuous process 

 of formation while their total number remains nearly constant, 

 there must be a corresponding consumption of them. 



The presence of atmospheric oxygen is indispensably re- 

 quisite for this active metamorphosis of the Ijlood, and one of 

 the results of this change is an excretion of carbon, which com- 

 bines with a portion of the absorbed oxygen, so as to develop a 

 certain degree of warmth. The probability that the chemical 

 process, which occui's during nutrition in the peripheral system 

 by means of the plasma, involves the absorption of oxygen, has 

 been already noticed. The importance of the presence of oxygen 

 for the perfect metamorphosis of the blood, and indeed for life 

 itself, is sufficiently obvious fi'om the cii'cumstance that the ces- 

 sation of the respiratory process is followed by immediate death. 



Although the respiratory process is as necessary for the active 

 metamorphosis of the blood as for the production of animal heat, 

 yet neither of these processes is to be referred to the lungs 

 alone, but to the whole peripheral system. If it were other- 

 wise, the temperature of the lungs would be much higher than 

 it actually is ; whereas, in reality the excess of temperature of 

 those organs is very slight, and may probably be sufficiently 

 accounted for by the more energetic action of the atmospheric 

 oxygen on the mass of the blood in these organs than in other 

 parts of the body. 



I cannot give any description of the manner in which the 

 blood-corpuscles are formed from the consumption of lymph-, 

 chyle-, and fat-corpuscles. Physiologists suppose that a capsule, 

 which at first is very thin, but subsequently becomes thicker 

 and thicker, is developed around the lymph-coq^uscle : this cap- 

 sule is filled with hsematoglobuhn, which at first is compara- 

 tively colomiess, but subsequently assumes a \dvid red tint. 

 We are perfectly unable to state where the first hsematoglobulin 



