Pathogenesis. Anatomical Changes. Symptoms. 677 



borliood of the vertebral canal (Decosse, Ohm, Frohner), or in 

 cases of suppurative inflammation in the mediastinum or neck. 

 According to Trasbot, inflammation may extend along the 

 course of nerves from nerve plexuses to the membranes of the 

 cord. This has been proved by Homen and Laitneu by the 

 injection of streptococci into the sciatic nerve; the meningitis 

 observed in one case of dourine may have been caused in this 

 way. The circumscril^ed spinal meningitis which often devel- 

 ops is not of much clinical importance as it is obscured by the 

 myelitis which develops at an earlier stage. 



Pathogenesis. The nerve terminals in the membranes, the 

 cord, and the nerve roots passing through them are irritated by 

 the hj^eremic dilatations of the vessels and the serous-celled 

 infiltration which soon follows. In the later stages the con- 

 ductivity of many of the nerve roots is lessened or even de- 

 stroyed. In addition to this, there is an extension of the in- 

 flammatory processes from the membranes to the superficial 

 layers of the cord itself. Intermixing of the toxic material with 

 the cerebro-spinal fluid, generally causes the extension of the 

 inflammation over a large area. 



Anatomical Changes. In addition to the marked conges- 

 tion of the vessels there is an exudate in the intermeningeal 

 space which is turbid or even mixed with flocculi of fibrin. The 

 vessels of the membranes may be surrounded by layers of fibrin 

 of variable thickness, producing an appearance of streaks of 

 pus. In many cases, the exudate is actually purulent. Not 

 rarely the fibrinous or purulent exudate involves the nerve 

 roots connected with the spinal cord. 



The presence of a clear serous fluid between the membranes is in itself no 

 proof of the existence of spinal meningitis. In animals in an advanced stage of 

 emaciation there are often large quantities of clear fluid in the subdural space, 

 but this is accounted for by the decreased resistance owing to the disappearance of 

 the epidural fat. 



Symptoms. The first symptom is increased sensibility 

 of those parts of the body, the nerve trunks of which pass 

 through the diseased membranes. As a result of this, the gait 

 is particularly cramped and cautious, and the animals liold the 

 vertebral column as motionless as possible and stiff. The sen- 

 sibility of the skin (hyperalgesia) is further shown by the 

 symptoms of pain exhibited if the skin be pinched or rublied 

 with the flat of the hand, especially in the direction opposed to 

 the lay of the hair, or if a sponge soaked in warm water be 

 placed in contact with the skin. The back is arclied, and the 

 animals become very restless, snap at the hand, and utter cries 

 of pain. Similar symptoms are exhibited if pressure be exert- 

 ed upon the muscles. In some cases, accurate investigation 

 shows that this increased sensibility is restricted to certain 

 parts of the body, a quarter, one half or a third of the body 



