322 



Prof. G. H. Darwin. 



[Apr. 30, 



blue-green to blue by nitric and sulphuric acids, and generally blue- 

 green with, iodine in iodide of potassium (in the solid state). 



On isolation of the yellow constituent of enterochlorophyll by 

 saponification and extraction with petroleum ether, I found that it 

 generally showed only one band, or sometimes two, but these bands 

 generally gave different measurements from those of plant chloro- 

 phyll. 



To see whether symbiotic algae were present in the organs yielding 

 enterochlorophyll, I examined fresh frozen sections, or portions of 

 the organ teased out in salt solution, but the results were negative. 

 On steeping such preparations, first in alcohol, then in weak solution of 

 caustic soda, and neutralising with acetic acid, and afterwards testing 

 with a solution of iodine in iodide of potassium and with Schultze's 

 fluid, I never obtained evidence of the presence of starch or cellulose. 

 Hence, apart from the absence of symbiotic algae under the microscope, 

 this result negatives their presence and also that of food chlorophyll. 

 The morphology of enterochlorophyll was studied in similar prepara- 

 tions, and on the whole it appears to be present dissolved in oil 

 globules and in granules, both of them enclosed in the epithelium 

 lining the liver tubes. It also occurs dissolved in the protoplasm of 

 the liver cells, and these appearances vary slightly in different 

 cases. 



It would therefore appear that enterochlorophyll is built up in the 

 organ containing it ; that it is a chlorophyll, of which there are 

 several in animals, and that it is composed of two constituents, of 

 which one resembles closely the corresponding constituent of plant 

 chlorophyll, while the other is generally slightly different, but that no 

 essential difference exists between the respective pigments is proved 

 by the fact that the constituents of both may be obtained crystallised 

 in the same form. 



In enterochlorophyll there is probably a more intimate union 

 between the constituents than in plant chlorophyll. 



All readings are reduced to wave-lengths, and the most important 

 spectra mapped in the accompanying charts. The appearance of 

 enterochlorophyll under the microscope in different cases is also 

 shown in the accompanying drawing, as well as the crystals referred 

 to above. 



III. " Note on a Previous Paper." By G. H. Darwin, F.R.S., 

 Fellow of Trinity College and Plumian Professor in the 

 University of Cambridge. Received March 19, 1885. 



The paper entitled " On the Stresses caused in the Interior of the 

 Earth by the Weight of Continents and Mountains " (" Phil. Trans.," 



