Specific Gravity and Luminescence in Noctiluca, etc. 247 



by electricity. As mentioned previously, a few shocks of an induced 

 current causes the protoplasm of a noctiluca to shrink away from the 

 membrane into a compact irregular mass; when again stimulated, the 

 irregular mass of protoplasm gives light, while the clear peripheral 

 area remains entirely dark. Also, in centrifuged noctilucas there is 

 a gradual motion of luminescence in a cell corresponding roughly with 

 the motion of the protoplasm as it resumes its normal position. These 

 granules in the protoplasm to which the luminescence may be traced 

 do not stain with neutral red nor with methylene blue ; there are other 

 granules, however, especially around the periphery of the cell, which 

 do stain with neutral red. 



It has not been possible to obtain two substances concerned with 

 light-production in Noctiluca, as in Pholas (Dubois, 1913, 1914), firefly 

 and Cypridina (E. N. Harvey, 1917), etc., one destroyed by heat (pho- 

 togenin) and the other thermostable (photophelein), notwithstanding 

 repeated efforts to demonstrate them. Only one substance respon- 

 sible for light-production in Noctiluca can be demonstrated, and this 

 substance occurs as granules and burns until it is all used up as soon 

 as it is brought into contact with atmospheric oxygen by crushing the 

 cells; this we may conveniently call photogenin. 



ANESTHETICS. 



Anesthesia may be defined as a temporary inhibition of some physio- 

 logical activity and includes a wide range of processes such as cell- 

 division, responses to stimuli of various kinds, Ught-production, etc. 

 Its chief characteristic is that the condition is reversible — that is, that 

 normal processes are resumed on removal of the anesthetic. The 

 anesthesia may be caused by various means — the constant electric 

 current, change of temperature, and many chemical substances. 

 Among the latter are the salts of Mg, Ca, and other metals, as well 

 as the more common Upoid-soluble anesthetics — chloroform, ether, 

 alcohol, etc. This study deals with the anesthesia of light-production 

 in Noctiluca by means of the hpoid-soluble anesthetics. 



The only previous work showing the definite anesthesia of light- 

 production in animals is that of E. N. Harvey (1915) on luminous bac- 

 teria ; he found that the light could be inhibited completely by various 

 alcohols and returned on dilution with sea-water. 



Of the various theories of anesthesia, that of Overton (1901) and 

 Meyer (1899) has received widest acceptance. According to this 

 theory, anesthesia is due to lipoid solubility, the anesthetic dissolving 

 in the lipoids of the cell. It has been shown by Overton that there is 

 a direct ratio between the narcotizing power of anesthetics and their 

 lipoid solubility — that is, the more soluble the narcotic in fat, the more 

 narcotic power it has and the smaller the amount necessary for anes- 

 thetizing. Just how the solution of the anesthetic in lipoids should 



