I do not know that the doctor who is the direct occasion of this paper was _grim_, nor do I imagine he ever dreamed of such an application of his paper as I purpose to make. I never met him; though he wore the gray and I the blue during a struggle wherein fate might easily have thrown us together. It was not until the autumn of '76 that I became aware of his existence, and then by a contribution of his to a medical magazine--the special copy of which was found amongst the multifarious waifs of a bookstall. I could not "decline the article," although I was then entering upon a field of labor that would leave little time for such quiet research as the old doctor's paper so powerfully suggested, so I bought the odd number, and fourteen years later I am making such use of it as my sense of its significance enforces. It is due Mr. A. J. Tafel to state that but for his most efficient services this paper of mine would never have been written. To his endeavors, stretching through some years, I owe the identification of the remedy, without which I should not have put pen to paper; and having secured this, from unimpeachable authority, too, he never rested from his labors until he had put in my possession dilutions of the poison itself. If, then, this _magis venenum_ shall prove itself _magis remedium_, most assuredly the _pars magna_ of its introduction is his. From the days of Dioscorides and Pliny to the present a venomous quality has been ascribed to "the fluid emitted from the orifice in the fangs of the arancidæ." That this quality was even lethal has been both believed and questioned. _Insect Life_, Vol. I., No. 7, pp. 204-211, Washington, 1889, contains "A Contribution to the Literature of Fatal Spider Bites," in which the credulity of mere medical observers and the emphatic incredulity of professed "entomologists and arachnologists" are dwelt upon, and concerning which its author cautiously concludes as follows: