812 THE POPULAR SCIENCE MONTHLY. 



and Animal Life," at least two important contributions to the same 

 subject have made their appearance. One of these, "written by Mr. P. 

 Geddes, of Edinburgh, may be found in " Nature " of January 2G, 

 1882. The other, from the pen of Professor E. Ray Lankester, was 

 published in the April number of the " Quarterly Journal of Micro- 

 scopical Science." 



The spectroscopic examination of animal pigments, a line of inves- 

 tigation in which Professor Lankester was one of the earliest observers, 

 has shed much light on these previously little known compounds, and 

 has opened a wide field for further research. Especially fruitful in 

 this direction was the announcement, perhaps a dozen years ago, that 

 various animal greens yield a spectrum identical or nearly so with that 

 furnished by chlorophyl, the common green coloring-matter of plants. 

 At once a host of interesting questions sprang up as to the occurrence 

 structure, and properties of " animal chlorophyl " all of which, how- 

 ever, culminated in this : Is the color " accidental " and unimportant 

 in animals, or has it rather some profound significance, such as attaches 

 to it when it is found in vegetable protoplasm ? 



It may well be considered as one of the fundamental truths of biol- 

 ogy that chlorophyl in vegetable substance is no insignificant intrud- 

 er. Though the exact method of its working is just now a matter of 

 much dispute, the broad fact of its usefulness is freely admitted ; in 

 one way or in another, chlorophyl aids in the economy of the vege- 

 table cell so that it feeds greedily upon the carbonic acid of the sur- 

 rounding air or water, and tears to pieces, for building up afresh its 

 own substance, compounds which, without chlorophyl, it would be 

 powerless to utilize, or which if utilized would be speedily sacrificed. 

 A long series of experiments, reaching from the time of Priestley to 

 the present day, uphold and strengthen this fundamental fact ; but, 

 among them all, the simplest is the most unique and the most pro- 

 nounced. If a piece of a green plant be immersed in water and ex- 

 posed to sunlight, bubbles of oxygen are given off, and analysis will 

 prove that carbonic acid has simultaneously disappeared from the 

 water. With plants not green, or with animals, the facts are re- 

 versed oxygen disappears and is replaced by carbonic acid. 



The green plants, then, exhibit a peculiar power, viz., that of split- 

 ting up carbonic acid, and of availing themselves for the manufacture 

 of starch, etc., of the carbon thus gained ; at the same time procuring 

 such a large supply of oxygen that they are able to reject a vast 

 amount over and above their own needs. In this respect they differ 

 from colorless plants and animals, and for this power they depend ex- 

 clusively upon the agency of chlorophyl. We have no evidence what- 

 ever that the chlorophyl of plants has ordinarily any other function. 



Very considerable interest has consequently been felt in the solu- 

 tion of the question, What significance (if any) has chlorophyl when 

 found in animals ? And since the only known use to which it could 



