Dec. 13, 1S77] 



NATURE 



119 



noticed by the three observers to whom we have referred, 



cannot as yet be adequately interpreted. 



Pathological anatomy then helps U3 a little in our 

 tempts to elucidate hydrophobia. Can we obtain better 

 iciults by reasoning upon the symptoms and course of 

 the disease from the standpoint of physiology ? Hardly, 

 but we may nuke the attempt. Physiology necessarily 

 cannot help us to understand the nature of the peculiarly 

 subtle poison which can lurk so long in the system with- 

 out betraying its presence by any symptom, but she 

 may help us in explaining the phenomena which it in- 

 duces. Of this poison we know as little, if not less, 

 than of the other poisons which are capable of inducing 

 zymotic diseases. Each of those diseases appears to 

 depend upon a definite luateries tnorbi, upon the presence 

 of whi h the peculiar phenomena of each dept-nd ; but 

 the periods which elapse between the introduction of the 

 poison and the manifestation of the disease varies in each 

 case, no less than the course and duration of the disease, 

 and the organs and tissues of the body whicli are affected. 

 Thus, in scarlet fever the poison induces changes in the 

 epitheliated surfaces of the body, manifested by the rash, 

 the sore throat, the acute kidney affection ; in typhoid fever 

 anatomical changes of the most obvious nature are wrought 

 in the alimentary canal, and lead to the special dangers of 

 the disease ; in typhus, again, the poison, whilst producing 

 changes in the general nutritioa of the body, and exciting 

 a specially-marked action upon the brain proper (as 

 evidenced by the marked affection of all mental pro- 

 cesses), produces no typical anatomical changes. These 

 diseases all illustrate the fact that the poison of each 

 zymotic disease affects certain tissues and organs of 

 the body, and it might be easily shown that it is by the 

 implication of particular functions that each of these 

 poisons usually induces death. Is there, in the case of 

 hydrophobia, any evidence that it affects specially any 

 particular organ of the body ? Yes ; a physiological 

 analysis of the disease reveals the fact that its symptoms 

 depend upon an affection of the nerve-centres, and espe- 

 cially of the medulla oblongata. 



These essential symptoms are — the spasmodic difficulty 

 of breathing, which depends upon a spasm of the inspira- 

 tory mechanism and a spasmodic affection of the group 

 of muscles engaged in deglutition. The nerve-centres 

 which preside over respiration and the co-ordinated 

 movements of deglutition are situated in the medulla 

 oblongata, and it is these centres which appear to be 

 peculiarly affected. The reflex excitability of this portion 

 of the nervous apparatus becomes first of all heightened 

 so that a stimulus applied to the mucous membrane of the 

 gullet, which in health v/ould give rise to a normal con- 

 traction of the muscles of deglutition, travelling on to the 

 morbidly irritable medulla, throws the centre presiding 

 over deglutition into a state of tonic spasm so intense as 

 to be acutely painful ; not confining its action to this one 

 centre, the stimulus is able to throw the contiguous 

 respiratory centre into a similar state of spasm, and the 

 patient runs the risk of suffocation because the move- 

 ments of the thoracic box, which are essential causes of 

 the passage of air into and out of the lungs, cease for a 

 time. The mechanism of suffocation in these cases 

 resembles that observed when the upper end of the 

 pneumogastric nerve is stimulated by a succession of 



strong induction shocks, except that in hydrophobia the 



abnormal effect is doubtless due not to the intensity of 

 the stimulus, but rather to the heightened excitability of 

 the nerve-centres implicated. Apparently a subtle animal- 

 poison acting upon an intensely vulnerable but limited part 

 of the nervous mechanism induces in it an action Fimilar in 

 kind to that produced by strychnia upon the. spinal cord. 

 Under the influence of this well-known poison the excita- 

 bility of the nerve-centres in the cord is heightened, so 

 that a stimulus reaching it by an afferent nerve which 

 would in the healthy unpoisoned condi ion lead to the 

 reflex and painless contraction of but a small group of 

 rnuscles, will be able to throw the nerve-cells of the whole 

 cord into intense activity, and as a re^^ult occasion the 

 characteristic and terribly painful convulsions of strych- 

 nia poisoning. There are, indeed, other facts besides 

 those previously mentioned which point to a state of irri- 

 tation and increased nervous excitability of the medulla 

 and contiguous nerve-centres. Thus it has been observed 

 that occasionally the pulse has been abnormally slow, a 

 result almost certainly due in these cases to an excitation 

 of the inhibitory centre in the medulla — of that centre 

 which exerts a moderating or restraining influence upon 

 the heart's action ; further, it not unfrequently happens 

 that towards the close of the hydrophobic stage, stimuli 

 which were at first only capable of inducing the spasms 

 of deglutition and inspiration, are able to bring on attacks 

 of general convulsions. Here we have a still further 

 extension of the effects of the irritation due to an 

 extension of the reflex excitability from the medulla to 

 the spinal cord. x 



Our analysis of the symptoms of hydrophobia reveals 

 that as a rule the spasmodic stage terminates before 

 death, which is not produced, as in strychnia poisoning, 

 by the mechanical result of the convulsions — suffocation 

 — but apparently by a more general, though we confess 

 unknown, action of the poison on the organism generally. 

 We know as little of the mode of death in this case as we 

 do in that of scarlet fever, or diphtheria, or typhus, each 

 one of which may produce death without leading to the 

 anatomical results which, at any rate in the case of the 

 two former of these diseases are their usual accompani- 

 ments. Zymotic poisons may indeed leave as few traces 

 of their action as the simpler and belter known poisons 

 such as prussic acid or morphia, so that whilst we cannot 

 disregard the local manifestations or changes which they 

 induce, and which of themselves are a frequent source of 

 danger, we must admit that they are in many cases — 

 nay in most cases — secondary in importance to the more 

 general phenomena which are the expression of the 

 poisonous influence affecting the. organism. 

 {7^ be co?t(inUid,) 



ANCIENT HISTORY FROM THE MONUMENTS 

 Ancient History from the Monuments. The History of 



Babylonia. By the late George Smith ; edited by A. 



H. Sayce. The Greek Cities and Islands of Asia 



Minor. By W. S. W. Vaux. (Society for Promoting 



Christian Knowledge, 1877.) 



THE Society for Promoting Christian Knowledge has 

 been doing a very useful work in acquainting the 

 public with the historical results of recent Oriental research 



