The Chemistry of Light-Production in Luminous Organisms. 227 



increasing the concentration above this does not increase perceptibly 

 the brightness. 



Each substance must be present in a definite small concentration to 

 produce light. This is m/32,000 for pyrogallol, 0.025 per cent for 

 H 2 O 2 , 0.1 per cent for dried blood, and 5 per cent for potato-juice 4. e., 

 5 parts pure potato- juice to 95 parts water. 



Note also, from tables 21 and 22, that very often the guaiac reaction 

 can be obtained when, under similar conditions, no light-production by 

 pyrogallol takes place. 



TABLE 21. 



2. SUBSTANCES TAKING THE PLACE OF OXIDASE, PYROGALLOL, AND H 2 C>2. 



Oxidase. Any plant extract containing strong oxidases, such as 

 occur in turnips, sweet potatoes, horseradish, etc., or any blood con- 

 taining hemoglobin, will give light with pyrogallol and H 2 O 2 . Apple- 

 juice, which oxidizes tannin, gives no light. Extracts of many inver- 

 tebrates were tried (Including insects, molluscs, annelids, crustaceans, 

 and echinoderms), but only those of Chiton, a tubicolous annelid (Lao- 

 nome japonica), and some polychsetes have thus far been found to give 

 light. The extract must be concentrated and the light-production is 

 probably due to hemoglobin, as it is obtained in many cases after the 

 extract is boiled. The substances in Chiton seem to come from red 

 filaments near the mouth (muscles ?) . Contrary to my earlier experi- 

 ments, which were performed with too -dilute extracts, I find that the 

 blood of a squid (Sepia esculenta) (containing hemocyanin) and the 

 orange blood of the Japanese lobster (Panulirus japonica) , will also give 

 light, and the light is somewhat brighter if the blood has previously 

 been boiled. The extracts of luminous animals never gave light with 

 pyrogallol +H 2 O 2 . Among these, bacteria, an annelid (Chcetopterus), 

 a squid (Watasenia scintillans), a crustacean (Cypridina), a protozoan 

 (NoctUuca), a pennatulid (Cavernularia), and the firefly have been tried. 



Inorganic substances which give light may be divided into three 

 classes: (1) insoluble precipitates, (2) colloidal metals, (3) solutions 

 of various salts. H 2 O 2 must always be added. The first two classes 

 probably act as true inorganic catalyzers. 



