ANATOMY AND PHYSIOLOGY OF NERVOUS SYSTEM. 



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3. THE ABDOMINAL REFLEX is a contraction of the abdominal 

 luscles caused by a sharp push of the finger. Its center lies between 



eighth and twelfth dorsal. 



4. THE EPIGASTRIC REFLEX. If the skin between the fourth, 

 ifth, and sixth intercostal spaces be irritated, contractions of the 

 ?ctus abdominis of the same side will follow. The center is between 

 ie fourth and eighth dorsal. 



5. SCAPULAR REFLEX. An irritation of the skin covering the 

 japulse may cause contraction of the shoulder-muscles. Its center 



between the seventh cervical and second dorsal nerves. 



Tendon Reflexes. 1. ANKLE-CLONUS. When the sole of the 

 >t is pressed upon by the hand, then the gastrocnemius contracts, 

 id if the pressure is continued there may be several clonic contrac- 

 lons. Ankle-clonus is never found in health. 



2. PATELLAR REFLEX. When a tap is made on the tendon of 

 quadriceps just below the patella, the foot jumps upward. 

 Jendrassik found that the patellar reflex could be increased if, 

 it the time of tapping the tendon, the patient squeezed his hands 

 Aether or clenched his jaws. This augmentation has been called, 

 >y Mitchell and Lewis, reinforcement of the knee-jerk. Bowditch 

 id Warren found that if the reinforcing act preceded the blow on 

 ie patellar tendon by 0.6 second, the knee-jerk was inhibited instead 

 )f being increased. Both reinforcement and inhibition of the reflex 

 ire supposed to be due to "overflow" in the central nervous system. 

 r hen the cortical motor-center for the foot of a rabbit was irritated, 

 icn the patellar reflex caused by stimulation of the paw was in- 

 cased, as shown by Exner. 



The knee-jerk is absent in locomotor ataxia, and exaggerated in 



lesions of the brain and of the lateral columns of the cord. This 



exaggeration is due to removal of inhibitory impulses' from the brain 



ravelling down the middle third of the lateral columns, as I have 



lown in the case of the ano-spinal reflex. 



ANTAGONISTIC MUSCLES. Sherrington has shown a relation to 

 between the tonic condition of antagonistic muscles; for ex- 

 iple, between the hamstrings and the vastus internus of the quadri- 

 extensor. Division of the hamstring muscles, or even section 

 )f their nerve, causes a great increase in the knee-jerk, elicited by 

 ipping the patellar tendon. Stretching the hamstring muscles or 

 reak stimulation of the central end of the cut nerve to the ham- 

 ig, abolishes the knee-jerk. Every sensory irritation which calls 



