_Lac caninum_ is a remedy of undoubted value, though not very thoroughly understood and consequently not very extensively used in this dread disease. And since a proving has never been made, and since we have to depend entirely upon clinical reports I feel it my duty to report a few cases in which a clear demonstration of the value of this remedy was made. CASE I.--Bruce McG., æt. 15, dark hair, gray eyes, spare habit, rigid fibre, nervous, quick, active, called at my office in the evening complaining of sore throat, worse on right side, and on swallowing. Headache dull and heavy, slight fever. Inspection revealed tonsils and fauces congested and angry looking. On right tonsil a patch of membrane the size of a split pea was seen. _Lycopodium_ 30x was given. The next morning the entire trouble seemed to have gone to the left side; with it had come, also, stiff neck and tongue; profuse flow of saliva; temperature 101 F. Membrane somewhat larger. _Mercurius ruber_ 30x was given. In the evening the trouble was worse again on right side, the membrane now entirely covering both tonsils, temperature 102 F. Limbs ached, back ached, and patient was restless. Remembering the symptom, "membrane alternates between right and left sides," and this having been so characteristic, I gave _Lac caninum_ in the 30th potency. Improvement began immediately and at the end of the third day the membrane was entirely gone and case discharged as far as medicine was concerned. CASE II.--Louisa McG., æt. 13, in temperament exactly like her brother, the preceding case. Was irritable and listless for two days, but owing to the fact that the fair began in a few days, to which she was determined to go, she did not complain. The third day, however, her mother noticed that she was truly sick and, there being a number of cases of diphtheria in town, looked into her throat. She found both tonsils covered with a membrane. I was called and as no other symptoms could be elicited I gave _Sulphur_ 30x and told them I would call again in the evening, which I did and found symptoms rapidly developing. Aching in all the limbs; headache; pain in the throat on swallowing; worse on the right side; neck and tongue stiff; membrane just the same. Temperature 101.5; same remedy continued. Next morning the membrane was the same, pain now in left side, throat internally and externally oedematous, fauces and uvula glossy or varnished in appearance. Temperature 102, urine scanty, no thirst. _Apis_ 30x was now given. In the evening pain back in right side again. Temperature 102.5. Membrane spreading; stiffness of neck and tongue more marked and saliva profuse. Not having seen the case till the membrane had quite generally formed, but the patient being in temperament like her brother and the pain shifting from side to side, as in his case, I decided to give her _Lac caninum_. Improvement began immediately and at the end of four days the membrane was entirely gone.