THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 655 



a very close and striking one, but, as a rule, the association was questionable, and 

 frequently some slight disturbance, such as giddiness, the symptom of an already- 

 existing disease, was the cause of the accident. Wohlwill requires the following 

 conditions before there is proof of a causal connection between disseminated sclerosis 

 and trauma : (l) that the individual was previously healthy ; (2) a not too short and 

 not too long interval between the accident and the first symptoms ; and (3) a some- 

 what severe trauma from which one might expect injury of the brain or cord. 



It has been already noted that in this investigation there was no evidence for the 

 existence of capillary haemorrhages, except those probably pre-agonal ones, due to 

 respiratory difficulties. There are few positive data for the further fate of spinal 

 haemorrhages, and from those which we have as to the length of time taken in the 

 absorption of cerebral haemorrhages it is necessary to be cautious as to the conditions 

 in the cord. The remains of such may continue to be evident for a very long time — 

 often with no sign of degeneration or softening around them. 



(b) Psychical Shock. — The influence of severe terror and other marked emotions 

 has often been related not only to the onset o± the disease, but to a relapse or the 

 aggravation of a present condition. A possible explanation may be found in the 

 sudden changes of the circulatory conditions in the nervous system occasioned by 

 such influences as act specially on the vaso-motor system. The profound influence 

 of the vaso-motor system in the production of disease has scarcely been recognised, 

 and in a later section its possible mode of action in disseminated sclerosis will 

 be considered. 



(c) Chills. — Krafft-Ebing has attributed considerable etiological significance 

 to chills. In forty out of a hundred cases he traced this factor, and represents 

 the relationship between the two in the contraction of the vessels favouring 

 ischaemic degeneration of nerve fibres in localised areas — especially if collateral 

 anastomoses were absent. 



In regard to cold, fatigue, and psychical influences, it is probable that these act 

 as immediate factors by lowering the vitality or the resistance of the individual or 

 in allowing, through vaso-motor influences, the emergence of a toxin already 

 circulating in the blood. In the -case of trauma, the possibility of the actual 

 rupture of capillaries or of lymphatics must be admitted, and the consequent 

 haemorrhages or the toxic lymph thus admitted in sufficient concentration into 

 the tissues will effect the primary degeneration of the nerve fibres and a secondary 

 proliferation of glia. 



(d) Exogenous Intoxications. — Oppenheim has laid special stress on the influence 

 of lead, copper, and zinc, also of alcohol and carbonic oxide, and has met with such 

 causes in eleven out of twenty-eight cases of disseminated sclerosis. He speaks also 

 of a toxi-pathic tendency inherited by the children of workers in lead and other 

 metallic poisons. Hoffmann, however, in an analysis of a hundred cases, found lead 

 present as a factor in only one patient. It is evident that some more general causal 



