The Japanese Artificially Induced Pearl

Abstract

I DIRECTED attention in my 1902 paper (Proc. Zool. Soc., March 4, 1902) to the resemblance between pearls and “the structures sometimes found in epidermoid tumours and atheroma cysts.” A pearl might be compared to the concentrically deposited ball of desquamated epithelial cells characteristic, I believe, of the latter, except for the fact that the pearl (like the normal molluscan shell-substance, and unlike the outer layer of the skin, and the nails, horns, hair, etc., in mammals) is not composed of cells, but secreted at the surface of cells.