March 27, 1914] 



SCIENCE 



463 



ing a uniform stain. Nothing is more strik- 

 ing than the way in which dead cells are 

 stained in this manner. Liver cells selec- 

 tively poisoned by chloroform^ and renal 

 cells killed by sublimate^ both permit an 

 immediate diffusion of the dye into them 

 and resultant stain; and even the nerve 

 cells, normally hostile to the entry of a single 

 trace of the dye, receive it similarly when 

 killed, an elegant example of which is fur- 

 nished by the anterior horn cells in experi- 

 mental poliomyelitis.^ When we tap the 

 cover slip over leucocytes swimming in 

 trypan-blue, mechanical injury to the im- 

 mediate subjacent cells invites instant 

 entry of the dye.^'' 



It is evident then that into the dead cell 

 a true diffusion takes place, but if diffusion 

 be acting at all in the case of those living 

 cells which react to the vital stain it is at 

 least seriously hampered. There is in fact 

 no reason for the identification of the vital 

 stain with a diffusion phenomenon. It is 

 significant that the cells which take the ben- 

 zidine dyes are predominantly those en- 

 dowed with powers of phagocytosis, a pro- 

 cess long known to be operating in the case 

 of particles from approximately 10 to 1 

 micron in size but it is not improbable that 

 the colloidal particles of the benzidine dyes, 

 whose dimensions must lie below a hun- 

 dredth of such size, are received into the 

 cell in an essentially similar way. Owing 

 to their comparative minuteness, however, 

 these particles are enabled to gain entry 

 into many cells quite incapable of receiving 

 larger ones. The fibroblast and mesothelial 

 stains are examples of this. Yet in none 

 of these cases does the cell, as it were, drink 



3 Experiments with Dr. Samuel J. Crowe, as 

 yet unpublished. 



* Gross, Beitr. e. path. Anat., Bd. 51, p. 528, 

 1911. 



5 MacCurdy and Evans, Berliner Med. Woch., 

 1912, No. 36. 



5" Evans and Winternitz as yet unpublished. 



in the dye particles, as it does the freely 

 diffusing ions of a salt solution. Nor in- 

 deed are the dye molecular-aggregates pha- 

 gocytized in the usual acceptation of the 

 term, for there is not merely a protoplasmic 

 flow around a foreign body. Countless ul- 

 tramicroscopic particles of the foreign body 

 are let into the peripheral protoplasm 

 and collected in the more central lying de- 

 pots which we can at last recognize under 

 the microscope as the dye granules. 



This moving together or centralization of 

 the dye in granules is not a reaction pecul- 

 iar to the dyes, for an identical phenome- 

 non is seen when colloidal silver is used, in 

 which the particles have dimensions also 

 considerably below the limits of ordinary 

 microscopic vision and far below the dimen- 

 sions of the intra-cellular granules in which 

 they are later agminated.* Yet we have 

 never hesitated to speak of the phagocyto- 

 sis of silver aggregates in this later case. 



We have to do then, in the case of cells 

 which are stained vitally by these dyes, 

 with a great host of elements scattered all 

 over the body, serving in some special or- 

 gans as the lining of blood and lymph ves- 

 sels, but in the great interstitial tissue of 

 the body without the vessels, equally abun- 

 dant, cells whose primary function seems 

 to be the engulfment of particles whose 

 physical dimensions fall within certain 

 limits. These scavenger cells, as it were, 

 rid the blood and tissue juices of many 

 kinds of useful and unuseful debris. How 

 they do this may still be difficult to explain, 

 but there seems no doubt but that their pro- 

 toplasm in contrast to that of epithelial 

 cells consists of a peculiar physical system. 



" Bechold {Zeitschr. f. chemie und Industrie der 

 Eolloide, 2 Jhrg., heft 1, 2) has determined that 

 the aggregates of collargol-Heyden have a diam- 

 eter of 20 fifi. They consist of aggregates of metal- 

 lic particles and particles of the schutz-kolloid to- 

 gether. 



