114 CARNEGIE INSTITUTION OF AVASHINGTON. 



or similar bases with the sulphonic acids of naphthols, amido-naphthols 

 and naphthylamines. The study has proven that the distribution of 

 these substances in the body and their anchorage in certain cells does 

 not depend on any precise chemical configuration of the dye molecule, 

 but rather on the physical state of their solutions. This generalization 

 would appear to be significant for other fields of inquiry, pharmacology 

 for example. The cells which are affected by these dyes are character- 

 ized by their power to absorb rapidly ultramicroscopic particles, whose 

 physical dimensions fall within certain limits. Inasmuch as these cells 

 are the great phagocytes of the body, and as there is no difference in 

 their behavior toward particles of successively large size until ordinary 

 microscopic dimensions are reached, we must consider that the act of 

 phagocytosis, now known to be effective through surface-tension phe- 

 nomena, operates in the case of the submicrons of certain colloids. 



The cells which react in this way include the endothelium in five 

 localities, viz, in the lymph glands, hemolymph glands, liver, bone- 

 marrow, and spleen. This should be known as a specific endothelium. 

 Its behavior is shared with the cells of the great serous cavities and the 

 wandering cells (clasmatocytes) of the connective tissues. These cells 

 must now be included under one great class. The fibroblastic cells 

 of the connective tissue react to a distinctly lesser extent, their behavior 

 toward the vital stain being sufficiently characteristic to clearly sepa- 

 rate them. It is of importance that the ordinary blood elements do not 

 react in this way. Dr. Evans has taken advantage of this fact to iden- 

 tify the role of cells concerned in the experimental production of various 

 acute new growths of tissue, studied in collaboration with F. B. Bowman, 

 Milton C. Winternitz, Roger P. Batchelor, and Katharine J. Scott. 



Other cytoplasmic peculiarities of cell types have been investigated 

 by Dr. Edmund V. Cowdry, who has examined the mitochondria of 

 resting and dividing cells and demonstrated an elective vital staining 

 of mitochondria in fresh blood-cells. 



The cytological studies of Professor Eliot R. Clark, of which a prelim- 

 inary publication has been made, have additional importance on account 

 of their bearing upon the problem of the histogenesis of the lymphatic 

 system. He has observed distinct nuclear differences in endothelial and 

 mesenchyme cells of chick embryos of the fifth to the eighth day, differ- 

 ences expressed by tinctorial and morphological details of the nucleoli. 



The nuclei of lymphatic and blood-vessel endothelium have either a 

 single nucleolus or a pair of nucleoli, which are definite discoid bodies, 

 sharply marked out from the remainder of the nuclear material with 

 clear-cut, rounded outlines. The single nucleolus varies much in shape, 

 according to the shape of the nucleus. These nucleoli have a distinctly 

 reddish color. The remainder of the nucleus has a rather pale, fairly 

 homogeneous granular appearance. The nucleus of the blood-capillary 

 is slightly smaller than that of the lymphatic and nearly always has 

 two nucleoli. The single nucleolus appears to be more common in the 



