OF THE CALABAR BEAN. 775 



the death of these nerves ? Such conditions should not exist when the causes of 

 interference with antagonism have been removed. I, therefore, venture (in common 

 with others, and notwithstanding the anatomical difficulties that exist) to 

 include an arrangement of contractile blood-vessels among the causes that 

 produce iridal movements. 



These blood-vessels will possess the function of erectile texture, and will act 

 either in harmony with the dilator or constrictor muscles, or independently of them. 

 The coincidence I have frequently observed between changes of blood-tension and 

 differences in the size of the pupil also leads me to support this view. At the same 

 time, the influence of an erectile tissue is not in itself sufficient to account for all 

 the pupil changes ; they can never be explained satisfactorily without also con- 

 sidering the effects of spinal and of cerebral motor nerves, operating probably on 

 radiating and circular muscular fibres whose action is independent of such tissue. 

 The cervical sympathetic appears to be the channel through which the nerves 

 that originate in the cilio-spinal region pass to the iris. Stimulation of this 

 region, or of the sympathetic nerve, produces dilatation of the pupil : and this 

 does not interfere with the supposition of the existence of a contractile vascular 

 network co-operating with a proper dilator muscle ; for then the blood-vessels 

 of this network, being governed by branches of the same nerves, would contract 

 along with the dilator fibres, and the result would be a diminution in the size of 

 the iris, and, consequently, a dilatation of the pupil. In the same way, division 

 or paralysis of the sympathetic would result in iridal expansion ; the contraction 

 of the pupil being caused by dilatation of the blood-vessels, assisted, it may be, 

 by the simultaneous contraction of a circular muscle. 



B. TOPICAL EFFECTS. 

 When applied to the Nervous System. 

 It is obvious that when a poison is applied during life to the substance of any 

 of the central nerve-organs, it will produce its specific action on the system in the 

 ratio of the absorbing power of the organ, and therefore very much in proportion 

 to the local blood supply. Other distinct effects are, however, frequently caused 

 by the concentrated form and other peculiarities of the preparation. The watery 

 suspension of physostigma extract caused no peculiar symptom when applied to 

 the cerebrum of mammalians, birds, or frogs ; and as its absorption was slow when 

 so exhibited, the constitutional effects were produced only after long periods. 

 When it was applied to the spinal cord of frogs, peculiar twitchings occurred in 

 the muscles directly connected by motor nerves with the part of the cord in contact 

 with the poison. These twitches soon ceased, and no movements were then 

 caused when this portion of the cord was galvanised. The first effect was 

 probably the result of local irritation merely, while the final paralysis was due 

 to a specific action of physostigma. 



VOL. XXIV. PART III. 10 A 



