ANIMAL PSYCHOLOGY IN FRANCE 449 



occurs sooner, the longer the exposure of the organism to Hght; 

 in the morning shocks continue to heighten sensibiHty for a 

 long time; in the evening they quickly produce a loss of sensi- 

 bility. Under the influence of shocks, we should have exhaus- 

 tion of certain active substances, but the organism is more 

 richly supplied with these substances in the morning than in 

 the evening. 



I studied chemical, physical, and mechanical sensibilisators, 

 but more particularly the last. I recognized among other points 

 that one can modify the sensibility of an organism merely by 

 changing its orientation to gravity: a mollusc (Littorina) with 

 its head downward has less visual sensibility than when it is 

 moving with head upward. This would correspond to an altered 

 distribution of active substances in the cells of the retina. I 

 also observed an effect of increased sensibility as a result of 

 increased surface of the body in animals whose bodies swell, 

 for instance the Veritillum ; and under the influence of increased 

 pressure or of weights carried by the animal: ants with a load 

 are much more sensitive to light than those which carry nothing. 



Finally, I pointed out that all these variations in sensibility 

 may be taken account of in the study of tropisms. 



Matisse ^' worked with the following species of animals : Sagar- 

 tia parasitica, Asterias riibens, Nereilepas jurcata, Arenicola pis- 

 catorimi, Sipunculus midus, Haminea navicula, Cardiuni edule, 

 Pectunculus glycimeris, Sepia officinalis, Eupagurus bernhardus. 



He took proper account in his experiments of the oscilla- 

 tions in sensibility and motor activity at different times. Cold 

 more or less rapidly and completely suspends the sensibility and 

 motor activity of organisms: between io° and 2° C. most of the 

 animals studied became insensible and inert. The functions of 

 nutritive life (respiration and circulation), however, were con- 

 tinued with sufficient intensity. In the cuttlefish the case is 

 different: as the life of response diminishes the functions of 

 vegetative life weaken; death occurred at 7° C. by respiratory 

 paralysis accompanying locomotor paralysis. The action of cold 

 is in general reversible ; the same is not true of the action of high 

 temperatures, which often produce the same effects as cold. 

 However, differences may be observed: at 34° C, Sagartia dies 

 in a few hours, in a state of contraction; at 2°, the anemone 

 expands, loses sensibility, but remains alive. All these facts 



