360 ANATOMY OF THE CENTBAL NEEVOUS SYSTEM. 



observation of such forms will be of prime importance for the question confronting 

 us. We also discover much as the result of wounds, sections and compressions of the 

 cord, as often arise from caries of the vertebrse, and tumors. 



Much less effective than pathology is the examination of animals. Compared 

 with pathologic processes occurring in the fine mechanism they affect, the neces- 

 sary experimental attempts are exceedingly coarse and bungling. 



We cannot, of course, in this work give even a short resume of the 

 valuable finds for which we are indebted to numerous researches made in the 

 pathology of the spinal cord. There are many excellent works in this line. 



Only a few especially important and well-established points should be 

 here mentioned. 



Disease of the posterior columns causes different symptoms according 

 to its location in them. Destruction of the entering posterior roots must 

 interrupt the entire sensory apparatiis they contain, entailing the loss not 

 only of every quality of sensation, but also of the reflexes, which, indeed, 

 are possible through the sensory paths. Then, also, the tendon-reflexes 

 disappear. Those degenerations of the posterior columns which do not affect 

 the entering nerve-roots, or do so but partially, run their coiirses without 

 special disturbance of cutaneous sensibility, although the muscular sense 

 seems invariably to suffer. The motor power is in nowise affected by disease 

 of these columns. 



If the gray matter of the ventral horns be destroyed by a disease-process 

 there ensues, as in the case of destruction of peripheral nerves, paralysis of 

 the muscles which derive their nerve-supply from the respective level of the 

 cord. To this paralysis is quickly added atrophy of the paralyzed mu.scles. 

 In this respect does it also resemble peripheral paralysis: viz., that the par- 

 ticular muscles react to the electric current exactly as if the supplying nerve 

 were severed. Since the nerve and its end-organ in the muscle are but proc- 

 esses of the cell, it is not difficult to understand this relation. 



From the last-described symptom-complex one will always be able to 

 diagnose an affection of the lower segment of the motor path. 



Entirely different signs appear if there be an interruption in the upper 

 segment of the motor path, the tractus cortico-spinalis. 



If the pyramidal tracts are diseased, voluntary movements are dis- 

 turbed or lost. In addition, the paralyzed muscles, or those which may be 

 only slightly weakened, show a permanent increase in tension, tend toward 

 contractures, and are much more irritable to mechanical stimuli than nor- 

 mally. Always, in the presence of these symptoms alone, or when met with 

 in conjunction with other symptom-complexes, one can, with entire cer- 

 tainty, accept the fact of a participation of the pyramidal tracts in the 

 disease. Not seldom has unilateral interruption to the pyramidal fibers been 

 followed by bilateral paresis and increase of muscular tension. 



There occur diseases of the primary (lower) and secondary (upper) 



