352 



JOHN F. I'DLTON, JK. 



process to drop off an atom of magnesium and add one of 

 iron than it is to build up an enormously complex molecule 

 such as the porphyrins present. 



If such a view is capable of experimental proof it will have 

 an important bearing upon the phylogenetic origin of animal 

 pigments ; it will give fair indication that many animal pig- 

 ments were derived originally from plant chlorophyll as the 

 result of some symbiotic association (perhaps for the purpose 

 of facilitating respiration) of an animal with a chlorophyll- 

 bearing organism — a condition probably similar to that found 

 to-day among the sponges and certain of the Protozoa. On 

 the basis of this theory it is interesting to speculate concerning 

 the origin of haemoglobin in the higher animals. Is it not 

 possible, for instance, that our blood-pigment is derived from 

 the chloropliyllous substances which are taken in " as food, 

 a condition not unlike that which the writer believes to exist 

 in tlie coelenterates '? The recent feeding experiments of 

 Biirgi and his co-workers (1919) indicate that such is the case, 

 for they give strong indication that the animal body is depen- 

 dent upon chlorophyll for the building of haemoglobin ; of 

 three sets of anaemic rabbits, one was fed alone upon a chloro- 

 phyll diet, the other upon iron pills, and the last group upon 

 a mixture of iron pills andgreenstuffs. The anaemic condition 

 of the first two groups was very slow to improve, whereas 

 the animals in the last group within a short time lost all 

 symptoms of anaemia and the haemoglobin content of their 

 blood came back to normal. This means that chlorophyll 

 with its four pyrrol groups is quite as necessary for the manu- 

 facture of haemoglobin as elemental iron. This conclusion 

 is further substantiated by Grigoriew (1919), who has repeated 

 Biirgi's feeding experiments with positive results. If this be 

 true, methods can very well be devised to control the formation 

 of haemoglobin in disease. 



What, then, must be the conclusion as to the origin of 

 pigment in the coelenterates '? In the first place the chyl- 

 aqueous fluid, which in function at least is the analogue of the 

 blood of higher animals, carries to the tissue the components 



