Haubner found that drying the saliva in thin layers rendered it non-virulent and Pasteur has shown that the rabbit’s medulla loses its virulence in 14 or 15 days when dried in contact with air, and apart from putrefaction. Such laboratory results must however be qualified by the facts recorded by Blaine, Youatt and others in which hound after hound died of rabies from living in a dry kennel in which a rabid animal had preceded them. Until we know something of the living germ itself of rabies, it is unwise to infer too positive results from experiments on that microbe, in what may be but one stage of its existence. The virus is very resistant to cold, having survived a temperature of −60° C. (−76° F.) for several hours (Roux), −10° C. (−14° F.) for ten months (Jobert). Virulence is destroyed however by a temperature of 48° C. (118.4° F.) in five to twenty minutes (Galtier). Light destroys the virulence in 14 hours at 30° to 35° C. (Celli), but encreased pressure has little effect on it (16 atmospheres, Nocard and Roux). Glycerine at room temperature preserves the medulla in its full potency for four weeks, but destruction ensues if it is heated (Protopopoff). An aqueous solution of iodine (6:100) destroys the virulence (Galtier), as does also citric acid, bromine, chlorine, sulphurous acid, the mineral acids and cupric sulphate. _Ratio of successful inoculation to bites of rabid animals._ As rabies is usually transmitted by the bite, it is well to note that not all the bites of rabid animals are effective. Of 183 dogs confined with and bitten by a rabid dog 91 contracted rabies; of 73 cattle bitten 45 became rabid; out of 121 sheep bitten 51 succumbed and of 890 persons bitten, 428 took hydrophobia. Of 440 persons bitten by rabid wolves 291 contracted the disease. The escape of such a large proportion is variously accounted for. Wolves naturally attack the face, throat or hands where there is no protection by clothing, and inoculation is therefore much more certain. Dogs, especially in cold weather usually bite man through the clothes which wipe off the virus from the smooth conical teeth before they reach the skin. Long haired animals are often protected in the same way. In other cases the bite is sustained on a very vascular part and the free flow of blood washes out the poison. In still other cases the rabid animal making a number of snaps in rapid succession comes to the last with the teeth wiped clean and harmless. Again the prompt washing or cauterizing of the wound tends often to protect against infection. Under favorable circumstances however every bite infects, and the writer has seen six animals, bitten in the same stable, all contract rabies, while a man bitten through the coat sleeve by the same dog, and cauterized an hour later entirely escaped. If the bites are multiple, deep and irregular, the danger is greater.