228 NORTH AMERICAN MUSTELID^E. 



venomous as that of a rattlesnake, slioukl so seldom resort to that mode of 

 defence, if it be his. 



"The resulting disease resembles hydrophobia more than it does the efifect 

 of ophidian venom. But here, as observed at the outset, the likeness is only 

 generic, while specifically there are marked difierences. These have pur- 

 posely been kept in the back-ground until now. And in giving a differential 

 diagnosis, I sliall avoid repetitious details, and combine facts gathered from 

 many sources with the close and accurate observations which Dr. Shearer 

 has put at my disposal. 



" 1. The period of incubation is alike in rabies canina and rahies mephitica. 

 That is, it is indefinite, ranging from ten days to twelve months, with no 

 opportunity meanwhile for subsequent inoculation. But during the incu- 

 bative period of B. mephitica, no perceptible changes take place in the con- 

 stitution as in hydrophobia. In only one instance was there unusual nerv- 

 ousness, and that might have been due to alcohol. In every case where 

 there was time for it, the wounds healed over smoothly and permanently, 

 and in several instances not even a scar was visible. In no case was there 

 recrudescence of the wound, always seen in hydrophobia. Indeed, there 

 were so few premonitions of any kind that, in most instances, the attending 

 physicians themselves supposed the ailment to be simple and trivial, until 

 the suddeu and fearful convulsions came on to ba^l'lie all their skill. 



"2. Characteristic pustules form in hydrophobia beneath the tongue and 

 near the orifices of the snb-maxillary glands. (See Aitkeu, Sci. and Pract. 

 Med., vol. i, p. 653.) These were not reported in a single case of B. mephitica. 

 Dr. Shearer looked for them carefully in all his cases, but did not find them. 



"3. The specific action of hydrophobic virus aflfects the eighth pair of 

 cranial nerves and their branches, especially the oesophageal branch, the 

 result being great difficulty in swallowing; and the motor nerve of the layx 

 [larnyx — sic'], causing sighing, catching of the breath, and difficulty in 

 expelling the frothy mucus accumulated in the throat. These invariable 

 accompaniments of B. canina are usually wanting in B. mephitica; the ex- 

 ceptions being in the case of the Swedish girl, who complained of pain in 

 her chest; and the young man, Dr. Janeway's patient, whose constriction of 

 the throat was decided, as well as his sensitiveness to water. Dr. Shearer's 

 patients had no such trouble. A taxidermist, who has seen four dogs die 

 from B. mephitica, in Michigan, says they did not seem to have any fear of 

 water, or other signs which he had supposed were characteristic of B. canina. 

 Ordinary hydrophobia, again, is marked by constant hypenesthesia of the 

 skin, so that the slightest breath of air will precipitate convulsions. But, 

 in B. mephitica, fanning the face affords relief, and even cloths dipped in 

 water and laid on the forehead were soothing ! 



"4. In hydrophobia the perceptions are intensified, so that even the deaf 

 are said to have their hearing restored ; the pupils are strongly dilated, im- 

 parting to the eyes a wild, glaring expression ; the spasms are tonic, i. e., 

 steady and continuous; the pulse is feeble; and delirium is occasionally 

 relieved by lucid intervals. But the symptoms are wholly different in B. 

 mephitica : there is oscillation of the pupil ; the spasms are clonic, i. e., 

 marked by rapid alternate contraction and relaxation of the muscles ; small, 

 but wiry radial pulse and rapid carotids ; positive loss of perception and 

 volition throughout, until delirium ends in persistent unconsciousness, 

 simul'aueously with cold perspiration and relaxation of the sphincters. 



