390 PROCESSES OF LIFE REVEALED BY THE MICROSCOPE. 



than themselves, insignificant and insiduous, but deadly. Now, to 

 guard the body against these living particles and the particles of dust 

 that would tend to clog the system, there is a vast army of amosba-like 

 cells, the leucocytes, that go wherever the body is attacked and do 

 battle. If the guards succeed, the organism lives and flourishes; other- 

 wise it dies or becomes weakene'd and hampered. This much was com- 

 mon scientific property three years ago, when one of our members (Miss 

 Edith J. Claypole) came to my laboratory for advanced work. I dis- 

 cussed with her what has just been given and told her that there still 

 remained to be solved the problem, What becomes of the clogging or 

 deleterious material which the leucocytes have taken up? These body- 

 guards are, after all, a part of the organism, and for them simply to 

 engulf the material would not rid the body entirely of it, and finally an 

 inevitable clogging of the system would result. The problem is simple 

 and definite; what become of the deleterious substances, bacteria and 

 dust particles, that get into the body and become engulfed by the leuco- 

 cytes? Fortunately for the solution of this problem, in our beautiful 

 Cayuga Lake there is an animal, the Necturus, with external gills 

 through which the blood circulates for its purification. So thin and 

 transparent is the covering tissue in these gills that one can see into the 

 blood stream almost as easily as if it were uncovered. Every solid 

 constituent of the blood, whether red corpuscle, white corpuscle, 

 microbe, or particle of dust, can be seen almost as clearly as if mounted 

 on a microscopic slide. (See Plate XV.) 



Into the veins of this animal was injected some lampblack, mixed 

 with water, a little gum arabic and ordinary salt, an entirely nonpoi- 

 sonous mixture. Thousands of particles of carbon were thus intro- 

 duced into the blood and could be seen circulating with it through the 

 transparent gills. True to their duty, the white corpuscles in a day or 

 two engulfed the carbon particles, but for several days more the leuco- 

 cytes could be seen circulating with the blood stream and carrying 

 their load of coal with them. Gradually the carbon-laden corpuscles 

 disappeared and only the ordinary carbon free ones remained. Where 

 had the carbon been left? Had it been simply deposited somewhere in 

 the system? The tissues were fixed and serial sections made. The 

 natural pigment was bleached with hydrogen dioxid, so that if any car- 

 bon was present it would show unmistakably. With the exception of 

 the spleen, no carbon appeared in the tissues, but in many places the 

 carbon-laden leucocytes were found. In mucous cavities and on mucous 

 surfaces and on the surface of the skin were many of them; in the 

 walls of organs were many more apparently on their way to the sur- 

 face with their load; that is, the carbon is actually carried out of the 

 tissues upon the free surfaces of the skin and mucous membranes, 

 where, being outside of the body, it could no more interfere in any way 

 with it. But what is the fate of the leucocytes that carry the lamp- 

 black out of the tissues? They carry their load out and free the body, 



