PHYSIOLOGY: A. R. MOORE 
599 
nine in increasing the sensitivity of the sensory-motor junctions of the 
spinal cord is definitely known. In a more general way the selective 
affinity of caffein, camphor and atropin for specific parts of the vertebrate 
central nervous system has been established. 
As an instance of the application of this method to the study of the 
nervous systems of other forms, Baglioni^ has attempted an analysis 
of the cephalopod gangha by means of strychnine and phenol. Strych- 
nine was found to be specific for the cerebral gangha and phenol for the 
mantle gangha. 
The writer recently has found that freshly hatched squid (Loligo peahi) 
furnish excellent material for demonstrating reactions of the type under 
discussion. These little animals show a dehcate sensitivity to the action 
of the substance used. Their response to stimulation is easily demon- 
strable in the muscular convulsions of tentacles, neck and mantle, and 
the spasms are in every case, except where specifically inhibited, accom- 
panied by a striking play of the chroma tophores. The cephalopod 
chromatophore is a globular sac containing either yellow, red or brown 
pigment. At rest these bodies appear as small dark spots, scattered 
inconspicuously over the surface of the mantle, head and tentacles. 
Muscle fibers attached radially to the chromatophore control its form. 
Contraction of these fibers stretches the sac into a sheet, so that the 
surface of a given chromatophore may be increased a hundred-fold by 
this mechanism. 
The result of strong stimulation, such as mechanical injury or the 
action of potassium chloride, is a series of clonic spasms of the entire 
musculature, invariably involving extreme extension of the chromato- 
phores. The play of brilliant color may therefore be used as an indi- 
cator of stimulation. If the precaution is taken to view the animals 
against a white background, the reaction can be followed with the 
naked eye. Details can be studied with the aid of the low power objective 
of the microscope. 
In carrying out an experiment, a half dozen freshly hatched squid 
were put into a Syracuse watch glass containing a solution of the sub- 
stance to be tested. In sufficiently dilute solutions the characteristic 
effects could be followed for an hour or longer. A strychnine sulfate 
solution (1 : 100,000) maintained the squid in a highly sensitive state 
for over an hour, so that a slight jar was sufficient to throw the animal 
into spasms and bring on the play of chromatophores over the entire 
body. 
When put into caffein solution (1 : 10,000) juvenile squid show rapid 
circus movements. The circular character of the course is due to the 
