Makch 27, 1914] 



SCIENCE 



451 



The staining with acid azo dyes then is a 

 physical phenomenon, and when we turned 

 our attention to the likelihood of other so- 

 lutions or pseudo-solutions giving an iden- 

 tical picture we are able to say that such 

 is indeed the case, for those excellent sus- 

 pensions of fine particles of gold, silver, 

 palladium and some other metals which are 

 called colloidal solutions eventually stained 

 an animal just as did our vital dye. This 

 effect has in fact been known for a long 

 time for the so-called argyria, a pigmenta- 

 tion of the mucous membranes of workers 

 concerned with silver salts, is a similar 

 storage of particles formed by the silver 

 when it meets the fluids in the body. 



It remains now to discuss briefly what 

 cells or tissues in the body are selectively 

 affected by these stains. We can do this 

 best by describing the autopsy of an animal 

 which has been injected, on two occasions 

 three days apart, with trypan blue and 

 killed the day following the last injection 

 when the animal with every appearance of 

 health is intense blue. The skin of the ab- 

 domen when stripped back is seen to be in- 

 tensely stained, but freshly spread prepara- 

 tions from the subcutaneous tissue show 

 that the color is only to a minor degree due 

 to the coloration of the fliiids, but mainly 

 to great numbers of small though dense 

 granular deposits in certain cells. The 

 larger and more striking of the cells possess 

 a large slightly irregular oval nucleus, and 

 an elongated cell body with frequent 

 though always sharply defined pseudopo- 

 dia or larger cell processes. Irregularly 

 scattered through the cytoplasm are the 

 granular deposits of the dye, and the larger 

 of these are always comprised in a vacuole 

 inside of which both larger and tinier frag- 

 ments are in liveliest Brownian movement. 

 We have identified these large, brilliantly 

 stained cells of the skin and connective 

 tissue of the body as the cells which have 



been designated variously by histologists 

 as the resting wandering cells (Maximow) ; 

 the clasmatocytes (Ranvier), the adven- 

 titia cells (Marchand) and the rhagiocrine 

 cells (Regaud). At the same time in smaller, 

 although more abundant cells, cells with 

 more regularly oval nuclei and with faintly 

 defined nuclear membrane and cytoplasmic 

 boundaries, in these cells are fine scattered 

 granules of the stain. These are, we be- 

 lieve, the most abundant and typical ceUs 

 of connective tissue and are probably those 

 designated as fibroblasts by the majority of 

 investigators. None of the blood cells nor 

 the endothelial cells of the capillaries of 

 the skin carry the minutest trace of the dye. 

 The muscles of the body, instead of their 

 customary pink hue, are greenish in color, 

 due to the infiltration in the minute con- 

 nective tissue septa of countless numbers 

 of these vitally stained cells of both types. 

 The peritoneal cavity contains a normal 

 amount of fluid which is pale blue in color 

 and in which are suspended many vitally 

 stained cells. The most brilliant of these 

 and the largest are those cells which have 

 been designated by Mechnikoff, Schott and 

 others as makrophages — cells which, spheri- 

 cal in shape, are covered with delicate pseu- 

 dopodia,and the cytoplasm of which is often 

 a frothy mass of vacuoles, in which are al- 

 ways particles of the dye. "We can trace 

 all transition stages from these cells to those 

 but slightly larger than lymphocytes, all of 

 them containing some inclusions of the 

 vital stain. 



The cells which line the peritoneum, the 

 mesothelial cells of Minot, possess in a per- 

 ipheral zone the fine granulations which 

 are characteristic of the cells of type 2 in 

 the skin. 



Of the peritoneal organs the liver and kid- 

 ney are undoubtedly the deepest stained, 

 for they are almost a blue black, a color due 

 in the liver almost exclusively to the inclu- 



