GENERAL REMARKS ON STAINING 75 



nucleus, which has very httle cytoplasm about it, is cyanophilous. 

 Strasburger claimed that there is no essential difference between male 

 and female generative nuclei, and subsequent observation soon showed 

 that within the egg the sex nuclei rapidly become alike in their re- 

 action to stains. 



Malfatti (1891) and Lilienfeld (1892-93) claim that these reactions 

 are dependent upon the amount of nucleic acid present in the struc- 

 tures. During mitosis the chromosomes consist of nearly pure nucleic 

 acid and are intensely cyanophilous, but the protoplasm, which has 

 little or no nucleic acid, is erythrophilous. There is a gradual transi- 

 tion from the cyanophilous condition to the erythrophilous, and vice 

 versa, the acid structures taking basic stains, and basic structures, the 

 acid stains. 



The terms "erythrophilous" and ''cyanophilous" soon became obso- 

 lete, and many claimed the affinity is for basic and acid dyes, rather 

 than for blue or red colors. That the terms were misnomers became 

 evident when a combination like safranin (basic) and acid green (acid) 

 was used, for the cyanophilous structures stained red, and the eryth- 

 rophilous, green. 



According to Fischer (1897 and 1900), stains indicate physical but 

 not chemical composition. Fischer experimented with substances of 

 known chemical composition. Egg albumin was shaken until small 

 granules were secured. These were fixed with the usual fixing agents, 

 and then stained with Delafield's haematoxylin. The extremely small 

 granules stained red, while the larger ones became purple. Since the 

 granules are all alike in chemical composition, Fischer concluded that 

 the difference in staining must be due to physical differences. With 

 safranin, followed by gentian violet, the larger granules stain red and 

 the smaller, violet; if, however, the gentian violet be used first, then 

 treated with acid alcohol, and followed by safranin, the larger granules 

 take the gentian violet and the smaller, the safranin. In root-tips 

 similar results were obtained. Safranin followed by gentian violet 

 stained chromosomes red and spindle fibers violet, while gentian violet 

 followed by safranin stained the chromosomes violet and the spindle 

 red. One often reads that chromosomes owe their strong staining ca- 

 pacity to nuclein, and especially to the phosphorus, but, according to 

 Fischer, this is shown to be unfounded, since albumin gives similar 

 results, yet contains no phosphorus, and is not chemically allied to 

 nuclein. 



