The fourth part of his commentary is taken up with certain conjectures, as he calls them, and some conclusions from his work. In this he suggests the use of electricity for the cure of certain nervous diseases, and especially for the treatment of the various forms of paralysis. The use of electricity for these cases had been previously suggested, and Bertholinus had told the story of patients who were utterly unable to move and who had recovered after having been in the neighborhood where a lightning-bolt had struck. To the minds of physicians of that time, this must have seemed proof positive of the curative value of lightning, and, therefore, of electricity, for paralytic conditions. The remedy was heroic, if not indeed positively risky, but its good effect could not be doubted. Unfortunately, as is always true in medical matters, the real question at issue in these cases is not so much the value of the remedy as the propriety of the diagnosis. Paralysis, in the sense of inability to use one or more limbs, may be due to many causes. There are a number of forms of functional or hysterical palsy, that is, of incapacity to use certain groups of muscles not dependent on any organic lesion, but upon some curious state of the nervous system which may pass away entirely, and which, indeed, seem to be dependent on the patient's state of mind. A number of so-called paralytic patients were cured by the earthquake in San Francisco; some are made to do the apparently impossible every year; they get up and walk because of the shock due to a fire or burglars. We know now that the electrical status of the individual is very carefully protected from disturbance by external electrical forces. What Galvani began has borne fruit in diagnosis more than treatment, so that his prophecy has been amply fulfilled. "The application of this method may throw light on the subject and experience may help us to understand it." Among his conclusions, Galvani hints that electricity may not only proceed from the clouds during electrical disturbances, but also may proceed from the earth itself, and that living beings may be affected by this. He suggests, therefore, that plants and animals may be influenced in their growth and in their health by such electrical changes. He adds the suggestion that there may be some intimate connection between electrical phenomena and earthquakes, and suggests that, in countries where earthquakes are frequent, observations should be made by means of frogs' limbs in order to see whether there may not be some definite change in the electrical conditions of the atmosphere before and during the earthquake. He seems to have had some idea that the curious feelings which at times come before an earthquake to human beings, though they seem even more noticeable in animals, may be due to this change in atmospheric electricity.[13]