45 8 TEXT-BOOK OF PHYSIOLOGY. 



becomes general, and it is propagated up and down the cord, so 

 that all the muscles of the body are thrown into action, the 

 medulla oblongata acting as a focus whence radiate all reflex 

 movements. 



Special Reflex Movements. Among the reflexes connected 

 with the more superficial portions of the body there are some which 

 are so frequently either exaggerated or diminished in pathologic 

 conditions of the spinal cord that their study affords valuable indi- 

 cations as to the seat and character of the lesions. They may be 

 divided into : 



1. The skin or superficial, and 



2. The tendon or deep reflexes. 



The skin reflexes are induced by stimulation of the skin and 

 mucous membranes e. g., pricking, pinching, 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 depends 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. 



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 of 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 ^ skin or superficial reflexes, though variable, are generally 

 present in health. They are increased or exaggerated when the gray 

 matter of the cord is abnormally excited, as in tetanus, strychnin- 

 poisoning, and disease of the lateral columns. 



The so-called "tendon reflexes" also are of much value in the 

 diagnosis of lesions of the cord. They are elicited by a sharp tap on 



