78 CARNEGIE INSTITUTION OF WASHINGTON. 



attained, the characteristics of the individual cells and of the cell 

 colonies remain stationary until degeneration of the culture takes 

 place; there is no further differentiation except cell division, which 

 is frequent. There is an interesting resemblance between the re- 

 ticulum of smooth muscle and that of endothelium, in that under 

 conditions of fixation they both exhibit fibrillse. This indicates the 

 presence of a considerable amount of contractile substance in endo- 

 thelium and provides an anatomical basis for the contraction of 

 capillaries. 



The completed study of Dr. Ruth S. Lynch, on the cultivation 

 in vitro of liver cells of chick embryos, has been published since our 

 last report and constitutes a description of another distinct cell-type. 

 Dr. Lynch succeeded in obtaining membrane-like outgrowths of liver 

 cells up to 27 micra wide. In her publication she has carefully de- 

 scribed and illustrated the histological character of these cultures and 

 the manner of growth and degeneration of the liver cells and the 

 associated tissues. 



Cytoplasmic Granules. 



Living protoplasm is characterized by the presence of a variety of 

 cytoplasmic granulations concerning whose composition and function 

 we know very little; that some of them play a fundamental part in 

 the activity of the cell, however, there can be no doubt. There are 

 (1) the specific granules normally present in and characteristic for 

 certain cells, such as the granules of leucocytes, the large granules of 

 eosinophile cells, secretion granules, and, widely differing from these, 

 the specific pigment granules of the pigmented cells and the fat glob- 

 ules and granules of fat cells; (2) the mitochondrial granular or rod- 

 shaped bodies which are present in all protoplasm and which are 

 apparently concerned with some fundamental process common to all 

 cells; (3) a newly recognized group of granules found in cultures 

 grown in media containing white of egg, to which reference will be 

 made later; (4) a group of granules and associated vacuoles which 

 stain selectively with neutral red. 



In the Year Book for 1919 I referred to a study by Professor Lewis, 

 in which he described the occurrence and behavior of neutral-red 

 granules and vacuoles in degenerating fibroblasts, reaching the con- 

 clusion that they constitute a part of the process of cell degeneration. 

 During the past year an additional study on the origin and functional 

 activity of these neutral-red granules and vacuoles has been published 

 by Miss R. E. Prigosen. Miss Prigosen adopted the method of 

 making film preparations of living subcutaneous connective tissue of 

 8 to 17 day chick embryos and placing them under abnormal con- 

 ditions, such as in media to which neutral red had been added or 

 from which oxygen was excluded. The cells were then studied until 

 their ultimate death. These experiments fully confirmed the previous 



