REFLEXES IN MAN 563 



movements are executed automatically, the brain may be actively en- 

 gaged in other directions. It must be remembered, however, that the 

 brain itself often works automatically, intelligent results occurring 

 without an appreciation of the mental processes by means of which 

 they are accomplished. Examples of this kind of action are often 

 afforded by remarkable players at chess or " lightning calculators." 



Certain purely reflex movements may be restrained by an effort 

 of the will, as is well known ; provided, always, that these be move- 

 ments that can be executed by voluntary effort. Nevertheless, if the 

 sensory impression is sufficiently powerful or is frequently repeated, it 

 often is impossible to control such movements by the will. Movements 

 that are never in themselves voluntary, such as the ejaculation of 

 semen, when excited by reflex action, can not be restrained by a vol- 

 untary effort; while the reflex act of coughing, for example, may be 

 measurably controlled. It is hardly proper to speak of inhibition of the 

 reflexes, in the sense in which the term " inhibition " is commonly used 

 in physiology, for the reason that probably there are no special inhibi- 

 tory nerves for these movements. 



Various reflexes are made use of in pathology as means of diagnosis. 

 The superficial reflexes are those produced by tickling the soles of the 

 feet or by exciting other parts of the skin. The most prominent of the 

 deep reflexes is the patellar reflex, or the knee-jerk, produced by per- 

 cussion of the ligamentum patellae. 



Reflexes in Man. The most important of the superficial reflexes 

 are the following : 



Tickling of the soles of the feet produces movements of the lower 

 extremities. In cases of paraplegia in which the properties of the lower 

 portion of the cord are retained, the reflex movements produced by 

 tickling the soles of the feet are often violent. 



When the skin is scratched over the gluteus, the muscle is thrown 

 into contraction. 



Scratching of the skin on the inner surface of the thigh produces re- 

 traction of the testicle on that side. This is called the cremasteric reflex. 



The muscles of the abdomen contract when the skin is scratched, 

 and the same occurs with the muscles of the back on stimulation of the 

 skin of that part. 



The deep reflexes are sometimes called tendon-reflexes. The 

 "knee-jerk" is produced by contraction of the quadriceps following a 

 smart blow on the tendon of the patella. 



The " ankle-clonus " is a contraction of the gastrocnemius when that 

 muscle is forcibly put on the stretch and maintained in this condition 

 for a short time. 



