Jl8 BIOLOGICAL LECTURES. 



There is one suggestion of some importance which flows 

 from this. 



That most living matter needs oxygen for the maintenance 

 of life is a well-established fact, but in what precise manner 

 this oxygen is ultimately used in the organism, is a question to 

 which we can give hardly any satisfactory answer at present. 



In the luminous cell of the fire-fly, in which the mechanism 

 of oxygenation is carried to its highest perfection, it is com- 

 paratively easy to trace the path of oxygen, and how it is used 

 in the living cell. The oxygen here simply combines with the 

 dead substance prepared in the cell. The value of oxygen to the 

 luminous function of the organism lies in its ability to combine 

 with the dead substance produced by the activity of the living. 

 Is it possible that the relation of oxygen to life in general is of 

 a similar nature ? Does the value of oxygen to life lie primarily 

 in its ability to combine with the dead substances, which exist 

 side by side with the living, in all cells ? The haemoglobin is 

 a complex iron compound found in the red blood-corpuscle. 

 Oxygen loosely combines with this compound and forms oxy- 

 haemoglobin. The oxygen in this new compound is given up 

 in the tissue through which the blood circulates, and the com- 

 pound returns back to the original haemoglobin, which, coming 

 back to the respiratory organ, combines again with the free oxy- 

 gen, and begins the role of oxygen-carrier again. Here, again, 

 the substance in the cell which combines with the oxygen is not 

 the living substance, but the dead material formed by the activity 

 of the cell. Professor Loeb suggests that it is possible that 

 the relation of oxygen to life may be of this nature in all cases. 



It may be that in the luminous cell of the fire-fly the method 

 of oxidation is carried out with a highly specialized apparatus, 

 and the result of oxidation of the dead material conveyed in 

 such a form as to affect the most delicate of our sense-organs, 

 and that the relation of oxygen to the life of the cell in gen- 

 eral is thus revealed here with simplicity and clearness unparal- 

 leled in the whole series of vital activities. At any rate, this 

 aspect of the question may not be devoid of interest when taken 

 in connection with the fundamental problem of the relation of 

 oxygen to living substance, or respiration, in which, some have 

 even maintained, lies hidden the whole mystery of life. 



