74-O CONDUCTING PATHS IN THE SPINAL CORD. 



If the gray matter is divided except for a small connecting band, this alone 

 will suffice to convey pain impressions upward. According to Schiff, however, 

 the transmission under such circumstances is delayed. Only after the gray 

 matter has been wholly divided does the conduction of all pain sensation from 

 the portions of the body below the level of the section cease. In this way the 

 condition of analgesia is brought about, while tactile sensibility persists if the 

 posterior columns are intact. A similar condition is not rarely observed in human 

 beings during incomplete chloroform-narcosis, and particularly during the narcosis 

 induced by the combined administration of chloroform and morphin. As these 

 poisons benumb the nerves transmitting pain sensations earlier than the tactile 

 nerves, those operated on maintain that they appreciate the operation as a tactile 

 impression, as pressure, etc., but not as pain. As the conduction of pain takes 

 place everywhere through the gray matter, and as, further, the excitation of pain 

 extends the more widely throughout the gray matter the more intense the painful 

 manipulation, the so-called irradiation of the pain impressions can be under- 

 stood. In the presence of severe pain, the pain appears to radiate widely from 

 its seat of origin. Thus, for example, in case of severe toothache beginning in a 

 given tooth the pain soon radiates to the entire maxillary region and even to the 

 entire half of the head. In contradiction of this statement Bechterew maintains 

 that the path for pain impressions is situated in the lateral columns, in the 

 rabbit, hen and dog. 



The impulses for spasmodic, involuntary, Uncoordinated movements 

 are transmitted through the gray matter and from the latter through 

 the anterior roots. 



Such transmission occurs, for example, in cases of epilepsy and as a result 

 of certain intoxications, for instance with strychnin, in cases of uremic intoxica- 

 tion and of tetanus. Also the convulsions associated with anemia and dyspnea are 

 transmitted downward from the medulla oblongata through the entire gray 

 matter. 



The impulses for widespread reflex convulsions are transmitted from 

 the posterior roots to the ganglion-cells of the gray matter, further 

 through the anterior horns and finally into the anterior roots, and under 

 conditions that have been described in the discussion of this variety of 

 reflex convulsions. 



Inhibition of the pathic reflexes is effected through the anterior column 

 downward and then in the gray matter to the connecting tracts of the 

 reflex organs, into which resistance is introduced. 



The vasomotors pass through the lateral columns and, after having 

 entered the ganglion-cells of the gray matter at a given level, leave the 

 spinal cord through the anterior roots. Later on, they approach vessels 

 provided with a muscular coat, either simply through the path for the 

 spinal nerves, or, more frequently, they pass through the communicating 

 branches into the sympathetic and from this to the vascular plexuses. 



Division of the spinal cord paralyzes all of the vasomotors below the level 

 of the section. Stimulation of the peripheral stump of the cord conversely causes 

 contraction of all of the vessels. 



Fibers having a pressor action enter the cord through the posterior 

 roots, then pass upward in the lateral column and undergo incomplete 

 decussation. 



Their final goal is the dominating vasomotor center in the medulla oblongata, 

 which thus they stimulate reflexly. Analogous depressor fibers must pass through 

 the spinal cord, although nothing concerning them is known. 



From the respiratory center in the medulla oblongata there pass 

 downward in the lateral column on the same side the respiratory nerves, 

 which, after reaching the ganglion-cells of the gray matter, pass through 

 the anterior roots into the motor nerves to the muscles of respiration. 



