HYDROPHOBIA. SO9 



of the body become more or less weakened, and death ensues without 

 any very marked irritative symptoms. 



In man the incubation period after infection varies from fifteen days 

 to seven or eight months, or even longer, but is usually about forty days. 

 When symptoms of rabies are about to appear, certain prodromata, such 

 as pains in the wound and along the nerves of the limb in which tlie 

 wound has been received, may be observed. To this succeeds a stage 

 ■of nervous irritabiUty, during which all the reflexes are augmented — 

 the victim starting at the slightest sound, for example. There are 

 spasms, especially of the muscles of deglutition and respiration, and 

 cortical excitement evidenced by delirium may occur. On this follows 

 ,a period in which all the reflexes are diminished, weakness and paralysis 

 are observed, convulsions occur, and finally coma and death supervene. 

 The duration of the acute illness is usually from four to eight days, and 

 •death invariably results. The existence of paralytic rabies in man has been 

 denied by some, but it undoubtedly occurs. This is usually manifested 

 by paralysis of the limb in which the infection has been received, and 

 •of the neighbouring parts ; but while in such cases this is often the first 

 symptom observed, during the whole of the illness the occurrence of 

 widespread and progressive paralysis is the outstanding feature. 



The Pathology of Hydrophobia. — In hydrophobia, as in tetanus, to 

 Tvhich it bears more than a superficial resemblance, the appearances 

 presented in the nervous system, to which all the symptoms are natu- 

 rally referred, are comparatively unimportant. On naked-eye examina- 

 tion, congestions, and, it may be, minute hsemorrhages in the central 

 nervous system, are the only features noticeable. Microscopically, 

 leucocytic exudation into the perivascular lymphatic spaces in the 

 nerve centres has been observed, and in the cells of the anterior cornua 

 of the grey matter in the spinal cord, and also in the nuclei of the 

 cranial nerves, various degenerations have been described. In the white 

 matter, especially in the posterior columns, swelling of the axis cylinders 

 and breaking up of the myeline sheaths have been noted, and similar 

 changes occur also in the spinal nerves, especially of the part of the 

 body through which infection has come. In the nervous system also 

 some have seen minute bodies which they have considered to be cocci, 

 but that they are really such there is no evidence. Nelis and van 

 Gehuchten have drawn attention to early and well-marked changes 

 occurring in the peripheral, cerebral, and sympathetic ganglia, especially 

 in the intervertebral gangha and in the plexiform ganglia of the pneu- 

 mogastric nerve, consisting in the invasion and ultimate destruction of 

 the nerve-cell protoplasm by newly formed cells derived from the 

 capsular membrane. The lesions are most perceptible upon the death 

 ■of the animal, although they can be made out if the animal be killed 



