CHEMICAL VARIABILITY 65 



met with phloroglucin and protocatechuic acid ; the 

 other is variable, and consists of potash united to 

 some fatty acid, so that while in all cases phloro- 

 glucin and protocatechuic acid are present, the third 

 element varies, and these variations are the cause 

 of the peculiarities which characterize each grape 

 colouring-matter ; or at least, if they are not the 

 cause, they are concomitant phenomena. Similar 

 facts have been ascertained by Prof. Gautier con- 

 cerning a chemical substance which is very abundant 

 in nature, and which would seem to be constant and 

 invariable. Chlorophyll, according to his investiga- 

 tions, is not identical among Acotyledons, Monoco- 

 tyledons, and Dicotyledons ; there are marked chemical 

 differences, marked variations in chemical constitu- 

 tion, and even between two species of two families 

 (Spinach and Mallow) there is a difference. Of 

 course these variations are not very intense, and the 

 different sorts of chlorophyll are always homologous, 

 but they are not identical. Similar instances are to 

 be met with among animals. While we commonly 

 speak of albumen, ossein, syntonin, and other com- 

 pounds of animal tissues, as being constant and 

 identical, direct analysis and investigation show that 

 all these substances, when considered among different 

 animals, do present common characters, which are 

 permanent and ubiquitous ; all possess also special 



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