THE SPINAL CORD AS A REFLEX CENTER 597 



in this case by an abolition of the reflexes and a general loss of irrita- 

 bility of the nervous structures situated posterior to the cut.^ A 

 partial division of the cord, however, is often recovered from without 

 permanent loss of function. 



In this connection, brief reference should also be made to the ex- 

 periments of Goltz,^ purposing to arrive at a definite conclusion re- 

 garding the function of the spinal cord by the method of total or partial 

 extirpation. In the mammals, the former procedure is not feasible, 

 for the reason that the phrenic nerves take their origin from its cervical 

 portion. Any interference with the phrenic nuclei would cause a 

 stoppage of the respiratory movements. Goltz, therefore, removed the 

 cord merely as far as its upper thoracic segment, special care being 

 taken to protect these animals against an undue loss of heat and other 

 injurious influences. Those surviving the operation, showed a com- 

 plete motor paralysis which eventually gave way to an atrophic condi- 

 tion of these parts. They also exhibited a complete sensory anesthesia, 

 and although their vasomotor and other autonomic functions remained 

 depressed for some time after the operation, the vascular tonus re- 

 appeared in a large measure. In addition it was noted that the 

 ordinary pelvic reflexes again assumed their original qualities. These 

 results indicate very clearly that the sympathetic system is relatively 

 independent of the spinal cord and other parts of the central nervous 

 system, because the digestive, secretory, circulatory and. excretory 

 organs eventually regained their functions after the destruction of the 

 cord. Various other symptoms, however, such as a gradual lowering 

 of the body temperature and a very decided loss of adaptation of the 

 parts formerly innervated by the destroyed portion of the cord, sug- 

 gested that the animal was no longer able to influence its autonomic 

 organs and to correlate their functions with those of other structures. 



The Automatic Activity of the Spinal Cord. — Having established 

 the fact that the spinal cord is an important seat of reflex action, it 

 should be noted that several of the centers situated within the domain 

 of the cord and bulb, are automatically active. Admittedly, an auto- 

 matic action finds its origin neither in volition nor in sensory impres- 

 sions of the ordinary intermittent type. Its cause must rather be 

 sought in an '4nner'' stimulus which arises in consequence of constant 

 and specific stimulations and renders the center self -inducing. The 

 question of whether the centers of the spinal cord possess automatic 

 qualities, must be answered in the positive and especially if the medulla 

 oblongata is taken to be a part of this structure. Thus, it is a well 

 known fact that the cardiac, respiratory and vasomotor centers are 

 composed of cellular elements which generate impulses rhythmically 

 in consequence of inherent stimuh. While it is entirely probable that 

 the centers situated in the more posterior segments of the cord 

 possess a much slighter automatic power than those just mentioned, 

 it must nevertheless be admitted that they generate impulses at regular 



1 Collier, Brain, 1904, 38. 



2 Pfluger's Archiv, Ixviii, 1896, 362. 



