SPINAL CORD. 187 



their study affords valuable indications as to the seat and character 

 of the lesions. They may be divided into 



1. Skin or superficial, and 



2. Tendon or deep reflexes. 



The skin reflexes, characterized by contraction of underlying 

 muscles, are induced by irritation of the skin e. g. } pricking, pinch- 

 ing, scratching, etc. The following are the principal skin reflexes : 



1. Plantar reflex, consisting of contraction of the muscles of the 

 foot, induced by stimulation of the sole of the foot ; it involves 

 the integrity of the reflex arc through the lower end of the cord. 



2. Gluteal reflex, consisting of contraction of the glutei muscles 

 when the skin over the buttock is stimulated ; it takes place 

 through the segments giving origin to the fourth and fifth lumbar 

 nerves. 



3. Cremasteric reflex, consisting of a contraction of the cremaster 

 muscle and a retraction of the testicle toward the abdominal ring 

 when the skin on the inner side of the thigh is stimulated ; it de- 

 pends upon the integrity of the segments giving origin to the first 

 and second lumbar nerves. 



4. Abdominal reflex, consisting of a contraction of the abdominal 

 muscles when the skin upon the side of the abdomen is gently 

 scratched; its production requires the integrity of the spinal 

 segments from the eighth to the twelfth dorsal nerves. 



5. Epigastric reflex, consisting of a slight muscular contraction in 

 the neighborhood of the epigastrium when the skin between the 

 fourth and sixth ribs is stimulated; it requires the integrity of the 

 cord between the fourth and seventh dorsal nerves. 



6. The scapular reflex consists oi a contraction of the scapular muscles 

 when the skin between the scapulae is stimulated; it depends upon 

 the integrity of the cord between the fifth cervical and third 

 dorsal nerves. 



The superficial reflexes, though variable, are generally present in 

 health. They are increased or exaggerated when the gray matter 

 pf the cord is abnormally excited, as in tetanus, strychnia-poisoning, 

 and disease of the lateral columns. 



The tendon reflexes, characterized by the contraction of a muscle, 

 are also of much value in the diagnosis of lesions of the spinal 

 cord and are elicited by a sharp blow on a tendon. The following 

 are the principal tendon reflexes : 

 i. Patellar reflex, or knee-jerk, consisting of a contraction of the 



