Page:Popular Science Monthly Volume 75.djvu/294

290 Is milk a living substance? It is a saline solution, containing sugar and albumen. Microscopically we find it swarming with the postmortem débris of epithelium cells that have undergone fatty degeneration. 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 constitutes 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 referred 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 Amœba 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 hemorrhage. 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 their amoeboid and phagocytic properties; and recently in a properly prepared solution containing 3 per cent, of sodium citrate and 1 per cent, of sodium chloride, B. C. Boss 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. Thus we see a living plasma is not necessary for the blood 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