672 DR JAMES W. DAWSON ON 



tricular walls is usually associated with such a change in the fluid. Borst has pointed 

 out that the terminal branches of the central arteries ramify on the ventricular walls, 

 and this localisation of the areas might equally be related to the vascular richness of this 

 region. The cell infiltration and proliferation around the sub-ependymal veins, which 

 constitute the path of return of the peri-ventricular circulation, would then again be 

 simply an indication of the resorptive processes consequent on myelin degeneration 

 and not a result of a peri-ependymitis. Lhermitte and G-tjccione come to the con- 

 clusion that the toxic agent in disseminated sclerosis is carried mainly by the blood- 

 stream, but that a part in the process must also be ascribed to the cerebro-spinal fluid. 



Extra Note. 

 The wide-reaching possibilities of lymphogenous infection in connection with the 

 elucidation of the etiology of some nervous lesions is well illustrated in the recent 

 work of Orr and Rows. These writers have kindly given the following account of 

 this yet unpublished work. They consider that the lymphogenous infections are 

 characterised by phenomena varying from a polymorpho-nuclear or polyblast cell 

 exudation in the acute processes to a plasma-cell reaction in the chronic, and that 

 peri-arteritis is an essential feature. On the other hand, when bacteria-laden capsules 

 are placed in the abdominal cavity — a position least likely to lead to infection of the 

 lymph sheath of the peripheral nerves — it is found that no peri-arteritic plasma-cell 

 formation occurs in the spinal cord. The changes so far observed have been as 

 follows: (l) hyaline degeneration of the vessel walls with hyaline thrombosis; 

 (2) neuroglia proliferation around the vessels ; (3) the nerve cells are practically 

 normal ; (4) there is no evidence of peri-arteritis ; (5) small areas of disseminated 

 sclerosis ; (6) a slight degree of myelin degeneration which varies in distribution in 

 the different levels of the cord ; (7) the sympathetic nerve cells in the abdominal 

 chain show chromatolysis. They are of opinion that the influence of the sympathetic 

 cannot be excluded, and that the view of a general intoxication cannot be sustained 

 as an explanation of these lesions owing to their patchy character. They incline to 

 the view that the involvement of the sympathetic mechanism here and there causes 

 dilatation and stasis in certain parts of the cord vessels, favours the formation of 

 hyaline thrombosis, and hence myeline atrophy and sclerotic areas. The work on 

 which these guarded conclusions is based is as yet far from complete, and I am deeply 

 indebted to Drs Orr and Rows for allowing me to refer to this view : its possible 

 significance in relation to the determining cause of disseminated sclerosis cannot 

 be overestimated. 



