the acilviiv ol' various bacillaiy parasites, affording examples of siuulry specific disorders. Tlic problem l">efore iis in all such cases is to determine, if we can, the ratio of the force of resistance to that of the infection. Too often, we have but to study the course of the disease in order to decide this point, and while treating the patient as we w^atch the contest,* we sometimes discover evidence of inhibiting factors which prove adequate to check the miscliief arising from parasitic invasion. We have an example of this in the case of a proclivity to gout which tends markedly to check tuberculous invasion, and when this occurs to
- A passage in Harvey's Anatomical Exercise (Ivii.) on the
Generation of Animals, affords a remarkable prevision on his part respecting the reaction of the bodily tissues to the intrusion of irritants. Referring to the effect of spider poison when introduced by a prick under the skin, he wrote : — " Erat tamen in cute quod discerneret, quippe eodem loco, ubi venenata punctio contigerat, subito sese in tuberculum contraxit, induitque mox ruborem, calorem, atque inflammationem, tanquam ad pugnam et nocentis mali expug- nationem se roboraret et accingeret." What have we here but a forecast of the modern researches of Metschnikoff and others upon the action of phagocytes in inflammatory foci ? The idea of a contest in the involved textures was, I think, singularly prophetic of the histological discoveries to be made some 230 years later, and displays the intuition of Harvey in his study and interpretation of the secrets of Nature, without any other aid than his simple vision.
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