Copland includes "difficulty of breathing" amongst the elements of angina pectoris. Trousseau does not regard this difficulty as real. "Although patients think they are going to be suffocated during a paroxysm, the chest is normally resonant on percussion, and if it be auscultated as they draw in breath again vesicular breathing is heard everywhere." Watson says, "the patient is not necessarily out of breath. It is not dyspnoea that oppresses him; for he can, and generally does, breathe freely and easily." Stokes is decided: "Respiration is _secondarily_ affected; there may be slight dyspnoea or orthopnoea, with lividity of the face, yet by an effort of the will (if the patient dares to encounter the pang this commonly produces) the chest may be pretty freely expanded, and the breathing relieved for a brief space; dyspnoea is not a primary symptom of angina." Eulenburg and Guttmann say, "Our own experience leads us to adopt Parry's conclusion, that the changes in the respiration are principally, perhaps even solely, due to the pain." Bristowe speaks of the sufferer as "fearing to breathe." We can readily see that the "apnæa" observed by Dr. Semple in Cases 1 and 5 had physical origin, but in Case 4 he says "apnæa was extreme; the respiration only occasional--gasping." This shows to what an extreme extent the action of the spider poison had gone--even to implicating the diaphragm; and it is noteworthy that Anstie records a case of angina pectoris (_Neuralgia and its Counterfeits_, p. 67, London, 1871), in which "there was so marked a catching of the breath as to make it almost certain that there was a diaphragmatic spasm." Of the changes in respiration accompanying angina pectoris we have, then, both the general, and the rarest, form, produced pathogenetically by the poison of _Latrodectus mactans_. IV.