778 PSYCHIC FUNCTIONS OF THE CEREBRUM. 



Heat is appreciated later than cold, pressure earlier than heat. The reaction-time 

 for the perception of odor, which naturally is dependent upon many circum- 

 stances, such as respiratory phases, draft, is from 0.2 to 0.5 second. 



Irritation of considerable intensity, increased attentiveness, practice, anticipa- 

 tion of familiar impressions shorten the time. According to Lange in the case of 

 the sensorial reaction after prepared attentiveness, the apperception coincides 

 with the perception. The muscular reaction, on giving the signal, may finally, 

 however, be converted also into a simple reflex. In the case of tactile impressions 

 those are most rapidly perceived that affect situations endowed with the greatest 

 acuity of the spatial sense. The time may be prolonged in the case of strong 

 irritants and in that of complex objects to be distinguished. The duration of 

 apperception for a number of from one to three figures was in observations of 

 Tigerstedt and Bergquist from 0.015 to 0.035 second. Alcohol and anesthetics 

 alter the time, occasionally shortening it, or they prolong it, in accordance with 

 the intensity of their effects. If two different impressions are to be recognized 

 psychically in rapid succession a certain interval of time is necessary, which for 

 the ear is 0.002 to 0.007 second, for the eye from 0.044 to 0.047 second, for the 

 tactile.organ of the finger 0.0277 second (for two electrical cutaneous stimuli from 

 0.022 to 0.056 second). 



During sleeping and waking the periodicity of the active and resting state of 

 the mind can be recognized. During sleep there is diminished irritability of the 

 entire nervous system, which is explicable only in part through fatigue of the 

 centripetal nerves, but is especially attributable in a peculiar manner to the 

 central nervous system. During sleep stronger irritation is required in order to 

 excite reflexes. During deepest sleep the psychic activities appear to be wholly 

 at rest, so that the sleeping person may be compared to a being with extirpated 

 cerebral hemispheres. Toward the time for awaking, however, psychic activities 

 may appear in the form of dreams, but in a manner differing from normal psychic 

 processes. They comprise either sensations of which the objective cause is want- 

 ing (therefore hallucinations), or volitional impulses or conceptions that usually 

 are not executed and that are for the most part absent in the healthy logic of the 

 thinking process during the waking state. Often, especially toward the time of 

 awaking, actual stimuli are interwoven with the dream-images and they may affect 

 various organs of special sense. Reduction in the activity of the heart, of the 

 blood-pressure in the arteries, of the amount of blood in the brain, of the irritability 

 of the motor cortical centers, of the activity of respiration, of gastric and intestinal 

 movement, in the .generation of heat, in the secretions indicates a lessening in 

 the activities of the respective nerve-centers, and the diminished reflex activity a 

 lessening in the activities of the spinal cord. The pupils during sleep are the 

 smaller the deeper the sleep, so that in deepest sleep they cannot be made to 

 contract on exposure to light. They dilate in response to sensory or auditory 

 stimulation and in greater degree the less deep the sleep. They attain their 

 greatest size at the moment of awaking. It appears that during sleep a state of 

 ritation ot the central organ exists through which increased activity of certain 

 sphincter-muscles, such as the sphincter of the iris and that for closure of the 

 eyelids is brought about. The soundness of sleep can be determined from the 

 intensity of the sound that is required to cause awaking. Thus, Kohlschutter 

 found that sleep at first rapidly, then more slowly deepens, and after an hour, 

 according to Monninghoff and Priesbergen after if hours, is most profound; then, 

 at first rapidly and later more slowly it becomes again shallow and finally several 

 hours before awaking continues in almost uniform shallow depth. External 

 or internal irritation is capable suddenly of diminishing the depth, although 

 renewed deepening follows. The deeper the sleep the longer it lasts 



ihe cause of sleep is the consumption of potential energy in the nerves princi- 

 pally in the central organs, which renders restitution necessary. Perhaps accumu- 

 lations of decomposition-products in the body (? lactates) induce sleep. The ad- 

 vent of sleep is favored by the removal as far as possible of all sense-irritations, 

 bleep cannot voluntarily be postponed indefinitely, or be interrupted The hypnotic 

 >t many narcotics is remarkable. Absolute sleeolessness causes death (in 

 the dog after one hundred and twenty hours), with reduction of temperature, 

 diminished reflex activity and changes in the brain 



H t ypl J? tism ' In connection with the subject of sleep reference should be made 



to the most important results of investigations into hypnotism or animal 



SJ!" ES ^ lscl sed b ^ th ? studies of Weinhold, Heidenhain, Griitzner, Berger 

 and others. As the cause of this condition Heidenhain considers an inhibition 



