CENTRAL NERVOUS SYSTEM. 663 



muscles whatever the stimulus. In these cases small segments of the body 

 will perform the locomotor reactions when the segments of the spinal cord 

 belonging to them are intact (Steiner). 1 Tarchanow has shown that beheaded 

 ducks can still swim and fly in a co-ordinated manner, and among mammals 

 (dog and rabbit) Goltz and others have demonstrated that if the lumbar region 

 be separated from the rest of the cord by a cut and the animal allowed to 

 recover from the operation, it will with proper care live for many months, 

 and not only are the legs responsive to stimulation of the skin, but the reflexes 

 of defecation and urination are easily induced by slight extra stimulation. An 

 instructive reaction occurs when such animal is held up so that the hind legs 

 hang free. When thus held the legs slowly extend by their own weight and 

 then are flexed together. The reaction becomes rhythmic and may continue 

 for a long time. It is assumed in this case that the stretching of the skin and 

 tendons due to the weight of the pendent legs acts as the stimulus, and in con- 

 sequence the legs are flexed. This act in turn removes the stimulus, and as a 

 result they extend again, to be once more stimulated- and drawn up. 



In man, as a rule, death rapidly follows the complete separation of any 

 portion of the cord from the rest of the central system, especially if the sep- 

 aration be sudden, as in the case of a wound. But Gerhardt 2 has recorded 

 the retention of the reflexes in the case of compression of the cord by a tumor, 

 the case having been under observation for four and a half years ; and Hitzig 3 

 a case in which a total separation between the last cervical and first thoracic 

 segments had been survived for as long as seven years. The principal reac- 

 tion to be observed in such cases is a contraction of the limb muscles in 

 response to stimulation of the skin, such as a drawing up of the legs when 

 the soles of the feet are tickled. No elaborate reflexes are, however, retained 

 in connection with the muscles of locomotion. In the normal individual 

 reflexes involving striped muscles are found in the tendon reflexes, of which 

 the knee-kick is an example, in winking, and the whole series of reflex modi- 

 fications of respiration, such as coughing, sneezing, and the like. 



The activities of the alimentary tract are examples of reflex actions in- 

 volving the peristaltic contraction of unstriped muscles in deglutition, defe- 

 cation, and similar peristaltic movements in other hollow viscera. So, too, 

 micturition, the cremaster reflex, emission, and vaginal peristalsis and the 

 reactions of parturition are to be classed here. Moreover, the entire vascular 

 system is controlled in this manner, the contraction and distention of the 

 small arteries being in a large measure in response to stimuli originating at a 

 distance ; while as a third group we have the glands, the activity of which is 

 almost entirely reflex. 



It thus appears that the reflex responses, namely, simple reactions unac- 

 companied by consciousness, are in man mainly given by the unstriped mus- 

 cle-tissue and by glands, and only in a minor degree by the striped muscles. 

 Moreover, while the typical reflex is a reaction over which we cannot exercise 



5 Die Functionen des Centralnemensystems der Fische, Braunschweig, 1888. 



1 Neurologische Centralblatt, 1894, S. 502. s Loc. ait. 



