63     A third mode of employing medicines in diseases has been attempted to be created by means of Isopathy, as it is called—that is to say, a method of curing a given disease by the same contagious principle that produces it. But even granting this could be done, yet, after all, seeing that the virus is given to the patient highly potentized, and, consequently, in an altered condition, the cure is effected only by opposing a simillimum to a simillimum.      To attempt to cure by means of the very same morbific potency (per Idem) contradicts all normal human understanding and hence all experience. Those who first brought Isopathy to notice, probably thought of the benefit which mankind received from cowpox vaccination by which the vaccinated individual is protected against future smallpox infection and as it were cured in advance. But both, cowpox and smallpox are only similar, in no way the same disease. In many respects they differ, namely in the more rapid course and mildness of cowpox and especially in this, that it is never contagious to man by mere nearness. Universal vaccination put an end to all epidemics of that deadly fearful smallpox to such an extent that the present generation does no longer possess a clear conception of the former frightful smallpox plague.      Moreover, in this way, undoubtedly, certain diseases peculiar to animals may give us remedies and medicinal potencies for very similar important human diseases and thus happily enlarge our stock of homœopathic remedies.      But to use a human morbific matter (a Psorin taken from the itch in man) as a remedy for the same human itch or for evils arisen therefrom is —— ?      Nothing can result from this but trouble and aggravation of the disease.