PLASTIDS AND CHONDRIOSOMES 117 



to the opinion of Pensa (1914), that there is every reason to regard them 

 as homologous in the two kingdoms. He finds plant and animal chon- 

 driosomes to be practically identical in morphology, reaction to fixatives 

 and dyes, and distribution in resting and dividing cells : any conspicuous 

 differences in arrangement seem to be due to the more pronounced 

 polarity of the animal cell. In both cases they are most abundant in 

 the active stages in the life of the cell. As the cell ages and becomes 

 fully differentiated, i.e., as cytomorphosis proceeds, they diminish in 

 number and may completely disappear. 



Physico-chemical Nature. With regard to the chemical and physical 

 nature of chondriosomes, Regaud (1908), Faure-Fremiet (1910), and 

 Lowschin (1913), working respectively on mammals, protozoa, and plants, 

 agree that they are chemically a combination of phospholipin and albu- 

 min. They closely resemble phosphatids, which are combinations of 

 phosphoric and fatty acids, glycerol, and nitrogen bases. Lecithin is 

 such a compound. Since chondriosomes are soluble in alcohol, ether, 

 chloroform, and dilute acetic acid, many of the fixing reagents commonly 

 employed in microtechnique destroy them: this accounts in part for the 

 fact that they were not observed in many familiar tissues until a compara- 

 tively recent date. They are well fixed by neutral formalin, potassium 

 bichromate, osmium tetroxid, and chromium trioxid (chromic acid) ; and 

 these, therefore, are the principal ingredients of the fixing reagents em- 

 ployed in researches upon chondriosomes. Examples of such fluids are 

 those of Altman, Benda, Bensley, Helley, Kopsch, Regaud, and Zenker. 1 

 Besides staining with hsematoxylin and several other dyes commonly 

 employed with fixed material, the chondriosomes show a characteristic 

 affinity for certain intra-vitam stains, such as Janus green B, Janus blue, 

 Janus black I, and diethylsafranin, the reaction with the first of these 

 being especially strong. After certain treatments the chondriosomes may 

 closely resemble the "chromidial substance," or granules of nucleo- 

 protein distributed throughout the cytoplasm in some cells. That the 

 two are not to be confused has been emphasized by Duesberg and by 

 E. V. Cowdry. According to the latter author (1916) chondriosomes are 

 "a concrete class of cell granulations," and may be provisionally defined 

 as "substances which occur in the form of granules, rods and filaments in 

 almost all living cells, which react positively to Janus green and which, 

 by their solubilities and staining reactions, resemble phospholipins and 

 to a lesser extent, albumins." 



Origin and Multiplication. The questions of the origin and multipli- 

 cation of chondriosomes are much debated ones. Certain cytologists 



1 For convenient summaries of the effects of various reagents upon chondriosomes 

 the student may refer to Kingsbury's (1912) paper on cytoplasmic fixation, E. V. 

 Cowdry's (1914) on vital staining, and N. H. Cowdry's (1917) on plant and animal 

 chondriosomes. 



