662 FUNCTIONS OF THE SPINAL CORD. [CH. XLVII. 



2. Deep reflexes or tendon reflexes. This is a most undesirable 

 name, as they are not true reflex actions. 



Superficial Reflexes. These are obtained by a gentle stimu- 

 lation, such as a touch on the skin ; the muscles beneath are 

 usually affected, but muscles at a distance may be affected also. 

 Thus a prick near the knee will cavise a reflex flexion of the hip. 



The most important of these reflexes are : 



a. Plantar reflex : withdrawal of the feet when the soles are 

 tickled. 



b. Gluteal reflex : a contraction in the gluteus when the skin 

 over it is stimulated. 



c. Cremasteric reflex : a retraction of the testicle when the 

 skin on the inner side of the thigh is stimulated. 



d. Abdominal reflex in the muscles of the abdominal wall when 

 the skin over the side of the abdomen is stroked ; the upper part 

 of this reflex is a very definite contraction at the epigastrium, and 

 has been termed the epigastric reflex. 



e. A series of similar reflex actions may be obtained in the 

 muscles of the back, the highest being in the muscles of the scapula. 



f. In the region of the cranial nerves the most important 

 reflexes are those of the eye (i) the conjunctival reflex, the 

 movement of the eyelids when the front of the eyeball is touched ; 

 and (ii) the contraction of the iris on exposure of the eye to light, 

 and its dilatation on stimulation of the skin of the neck. 



Tendon Reflexes. When the muscles are in a state of slight 

 tension, a tap on their tendons will cause them to contract. The 

 two so-called tendon reflexes which are generally examined are 

 the patella tendon reflex or knee-jerk, and the foot phenomenon or 

 ankle-clonus. 



The knee-jerk. The quadriceps muscle is slightly stretched by 

 putting one knee over the other ; a slight blow on the patella 

 tendon causes a movement of the foot forwards, as indicated in 

 the dotted line of fig. 490. This phenomenon is present in health. 



Ankle-clonus. This is elicited as depicted in the next figure : 

 the hand is pressed against the sole of the foot, the calf muscles 

 are thus put on the stretch and they contract, and if the pressure 

 is kept up a quick succession or clonic series of contractions is 

 obtained. This, however, is not readily obtained in health. 



These phenomena are not true reflexes ; the time that inter- 

 venes between the tap and the response is so short that they must 

 be due to direct stimulation of the muscles or of their tendons. 



Nevertheless, the idea that they are reflex is supported by the 

 following facts : 



i. There are nerves in tendon. 



