I have cited this case at full length in order to present the _evolution of the symptoms_, on which alone depends the resemblance of the action of the poison to the chief symptoms of an attack of angina pectoris--a closer resemblance than half a lifetime of somewhat wide reading has enabled me to find in the effect of any other noxious agent. In fact, after much searching, I find this case to be unique. In other cases of spider bite I can find evidence that assures me of its genuineness, but, to my knowledge, its _order of symptom evolution_ is as solitary as it is singular and significant. This feature of _uniqueness_ will cause many to regard it with suspicion. I think they will do wrong; for some experience in proving work has taught me that one positive result from a drug out-weighs any number of negative. In the case of _Latrodectus mactans_ we shall find, from other poisonings, that, as a rule, it displays an affinity for the præcordial region as the _locus_ of its chief attack; and having assurance of that fact, we shall not find it difficult to accept a clue from even a solitary instance. Of the remaining cases in Dr. Semple's paper I shall cite only the symptoms, and be it observed that in all the cases as here given the italics are my own. CASE 2. A man "was bitten in the groin, and complained of only a slight prickling and itching at the spot where he was bitten, but was complaining [when Dr. S. saw him] of _severe abdominal pain_, with _nausea_, and a _sinking sensation at the epigastrium_; and his _pulse_, in a few minutes after the bite, had already become _quick and thready_; and the _skin very cold_." The man soon recovered under ammonia and whiskey--two quarts of the latter produced no symptoms of intoxication. CASE III. A lad of eighteen years of age. "There was no pain, but only itching and redness at the part bitten at first; but _violent pain soon commenced there_ [on the back of the left hand] _and extended in a short time up the forearm and arm to the shoulder and thence to the præcordial region_." CASE IV. "A tawny woman [daughter of a quadroon mulatto woman] about twenty-two years old, the mother of two children." "Found her _apparently moribund_; her _skin_ as _cold_ as marble; _violent pain extending from the bite on the right wrist up the forearm and arm to the shoulder, and thence up the neck to the back of the head on the right side_; more _violent pain in the præcordia_, _extending thence to the shoulder and axilla on the left, and down the arm and forearm to the ends of the fingers_, and _this extremity partially paralysed_; added to this, _apnæa was extreme; the respiration only occasional--gasping_; the _pulse could not be felt in the left radial_, and I was not sure that I felt it in the right."