BiRROAvs: Study of Body Cells. 483 



pcriocl. Muscle may contract for a time without oxygen. J. Loeb^^ 

 has found that oxygen is nceessary to preserve «the structure of the 

 fertilized egg. These experiments of J. Loeb also indicate that the 

 metabolic reaction may proceed without oxygen. That the same 

 is true for the animal colls has long been known by pathologists. 

 Cut off the blood supply from any part and it undergoes a coagu- 

 lative necrosis. These observations suggest strongly, therefore, 

 that oxygen plays a necessary but probably a secondary role in this 

 reaction. It acts to remove certain products of the primary reaction 

 rather than enter into it. 



All chemical reactions, as it is now fully appreciated, are governed 



not only by the concentration of reacting substances, but also by the 



concentration of one or all of the products formed. Equilibrium for 



a simple reversible reaction is expressed in the following formula: 



A + B + C + . . . = A'4-B' + C' + . . . 



In the animal organism growth is not determined by food any 

 more than it is determined by oxygen, but by other unknown factors. 

 Bardeen showed that planaria regenerate their parts when starved as 

 when they are fed.^"* Morgan found that salamanders regenerate 

 their legs as rapidly when starved as when fed.^^ The difference is 

 tiiat the starved animals suffer marked emaciation and a general 

 atrophy of their organs. 



The above observations of the connective-tissue cells indicates 

 clearly the existence of a previously unrecognized product of cell 

 metabolism which is evidently insoluble in liquid medium, but 

 rapidly adsorbed and chemically combined with fibrinogen. This 

 substance, which I shall designate as "L," is also an active blood 

 coagulant. It is something, therefore, which is insoluble in water, 

 but capable of combining with fibrinogen to form an insoluble com- 

 bination, fibrin. It acts in every regard, therefore, like the lipoid 

 fraction of the blood coagulant recognized by Woolbridge^^ and 

 recently carefully studied by Mills. ^'^ This fraction is a phospholipin 

 or a group of such bodies. 



In a recent series of experiments^ I undertook, therefore, to 

 ascertain more carefully the exact relation to this substance of the 

 general chemical changes of these cells. These cells had apparently 

 become inactive after they had come to rest in the clotted fibrin. 

 They had laid for months in this inactive state and in the presence of 

 oxygen. When removed to fresh medium they had again become 

 actively migrating cells. I removed the oxygen from about these 

 cells during their movement and also after they had come to rest. 



