730 THE SPINAL REFLEXES. 



the upper dorsal region, but some time must have elapsed after the section so 

 that the primary irritation of the lesion (so-called shock), which at first has a 

 reflex-inhibiting effect, may subside. Young mammals exhibit reflex activity for 

 some time even after decapitation.* 

 The coordinated reflexes include: 



1. Protective movements and movements of escape are observed in decere- 

 brated or decapitated frogs and turtles, as well as the removal of acids when 

 applied to the skin, resistance to fixation-instruments, etc. All of these move- 

 ments are executed apparently with deliberation and with the employment of 

 the most serviceable groups of muscle, so that Pfliiger was led to attribute them 

 to a spinal consciousness. Even excised portions of eel turn away from an intense 

 irritant such as a flame. Also the tail of a decapitated triton, lizard, salamander, 

 eel, or adder submits to gentle stroking, but turns away from intense irritation. 



2. Goltz's croaking experiment, which consists in the croaking of a decere- 

 brated frog when the skin of the back is stroked. 



3. Goltz's embracing experiment: The portion of the trunk of a young male 

 frog between the skull and the fourth vertebra, particularly during the breeding 

 season, embraces every solid body that comes in contact with the skin of the chest 

 and exerts a slightly stimulating effect. 



In the intact animal the stimulating irritant consists in the degree of fulness 

 of the male seminal organs. The reflex immediately ceases after slight irritation 

 of the optic thalamus. 



4. In warm-blooded animals (dogs) the following are among the coordinated 

 reflexes related to the posterior divided extremity of the cord: Scratching of tickled 

 portions of the skin with the hind-paw, as in normal animals; the movements 

 necessary for the evacuation of the bladder and the rectum, for erection and 

 the act of parturition, the coordinated movements of the feet and the tail in 

 decapitated ducks and pigeons. Coordinated reflexes simultaneously in widely 

 separated segments of the cord appear as a rule no longer .to occur after removal 

 of the medulla oblongata. For this reason it is believed that the medulla may 

 contain a complex organ of higher order connecting the different reflex areas in 

 the spinal cord (by white fibers) . 



5. In man coordinated reflexes occur also during sleep, as well as in comatose 

 states. 



By far the majority of the movements executed unconsciously during the 

 waking state, or when the mental activities are otherwise intently engaged, must 

 be included among the coordinated reflexes. Many complicated movements must 

 first be learned before they can again unconsciously be executed harmoniously 

 as coordinated reflexes, such as dancing, skating, and riding. Coughing, sneezing, 

 and vomiting are among the coordinated reflexes emanating from the spinal cord 

 and the medulla oblongata. 



With reference to the peculiarities of the reflexes the following points 

 are noteworthy: 



1. The reflexes can be elicited more readily and in more complete 

 degree when the stimulus is applied to the specific end-organ of the cen- 

 tripetal nerve, rather than to the trunk of the nerve itself . 



2. For the production of a reflex movement a stronger stimulus is 

 required than for direct stimulation of the motor nerve. The reflex 

 movement induced by a stimulus of adequate intensity appears at once 

 as a moderately strong contraction, which does not increase in intensity 

 with increase in the intensity of the stimulus. 



3. A reflex movement is of shorter duration than the same movement 

 executed voluntarily. Further, its occurrence after the moment of 

 irritation is distinctly delayed, the interval until the appearance of the 

 muscular contraction (in the frog) being twelve times as long as that 

 required for conduction through the sensory and motor nerves. The 

 spinal cord thus interposes resistance to the rapid passage of the impulse. 



The reflex time (that is the time required for the transference of the impulse 



within the ganglion-cells of the spinal cord) is in the case of closure of the eyelids 



man 0.042 second, in the frog on an average in various muscles from 0.008 



