2 9 o THE POPULAR SCIENCE MONTHLY 



Is milk a living substance? It is a saline solution, containing 

 sugar and albumen. Microscopically we find it swarming with the post- 

 mortem debris of epithelium cells that have undergone fatty degenera- 

 tion. It is the fatty dust into which these dead cells have crumbled 

 that rises to the surface as cream and when amassed in the churn con- 

 stitutes the butter of commerce. Milk is emphatically a dead material. 



What of that milky emulsion we call chyle? We can not say it is 

 alive in the intestine ; nor does it become so in the thoracic duct, nor in 

 the subclavian vein. Neither does mingling with the blood give it life. 

 It is dead. 



What of the blood itself? Commonly we speak of it as being 

 "warm with life." Not so in cold-blooded animals. Again, it is re- 

 ferred to as the " vital fluid/' the " life-blood " ; and we say : " the 

 blood is the life thereof." So it is, in the sense that we can not live 

 without it, and if we lose it by hemorrhage we die. Nevertheless, the 

 blood is not alive. Its corpuscles are, but the plasma in which they 

 float is not living. This plasma is the natural habitat of the living 

 corpuscle (much in the same way as a pond of water is the natural 

 habitat of Amoeba proteus), but it is not alive. 



Can our blood corpuscles live in a dead plasma? It is not very 

 long ago that in cases of hemorrhage we injected into the blood vessels 

 large quantities of cow's milk; now-a-days we inject salt solution. In 

 some cases we inject so much of these dead fluids that the quantity may 

 exceed that of the normal blood plasma left behind after the hem- 

 orrhage. Hence we know by actual experiment, in these cases, that 

 the larger part of the blood plasma mixture is not alive. 



Furthermore, human leucocytes have been kept alive in normal salt 

 solution outside of the body for many hours, retaining all tbeir 

 amoeboid and phagocytic properties; and recently in a properly pre- 

 pared solution containing 3 per cent, of sodium citrate and 1 per cent, 

 of sodium chloride, E. C. Eoss has kept human leucocytes three days 

 alive and has caused them to protrude and retract the most remarkably 

 long pseudopodia so that they actually resembled squids, or tarantulas. 1 

 Thus we see a living plasma is not necessary for the bloffd corpuscles: 

 they flourish in a dead one. The blood plasma is not alive. 



In the days of venesection we were taught that the last act of vitality 

 in blood when drawn from the body was its coagulation, but is this 

 really any more a vital process than the clotting of sour milk? I 

 think not. 



In the same category with milk and blood plasma, we must place 

 lymph, the fluids in the pleura, pericardium, peritoneum and synovial 

 sacs, and also the cerebro-spinal fluid ; none of them is alive. 



It might be supposed that the delicate structures of our central 



1 London Lancet, January 30, 1909, p. 314. 



