(_b_) It may be indirect, i.e. latent; this time also with some concurrence on the part of the subject. This seems more frequent. (_c_) Finally, it may in exceptional instances be either mediate (delayed) or immediate, even without the subject's being advised beforehand of the action. * * * * * Here, then, are the probable conditions; also the state of the agent and percipient. Now what about the _connecting links_? Here we come to the heart of the problem. I shall be as brief as possible, since we cannot pretend that the problem is yet solved. I merely offer a few suggestions, some original, others advanced before by writers on these subjects.[44] In order to obtain a specific action we must employ a specific instrument: a telephone for a telephone; a brain for a brain. Every living thing is a dynamic focus. A dynamic focus tends ever to propagate the motion which is proper to it. Propagated motion becomes transformed according to the medium it traverses. A force may be transmitted or transformed. In an identical medium there is only _transmission_. In a different medium there is _transformation_. A dynamic nucleus, in propagating its motion, sends it out in every direction; but this transmission becomes perceptible only on the lines of least resistance. A process that is at once chemical, physical, and psychical goes on in the brain. A complex action of this kind is propagated through the grey matter, as waves are propagated in water. Regarded physiologically, a thought is only a vibration, probably, which does not pass out of its appropriate medium. It is propagated, and it must be along the motor nerves, since science admits no other route. But the _thought itself_ does not radiate; it remains "at home," just as the chemical action of a battery remains in the battery; it is represented abroad by its dynamic correlate, called, in the case of the battery, a _current_; and in the case of the brain, I know not what; but whatever its name may be, it is the _dynamic correlate of thought_. Thought, therefore, is dynamic. Thought is transformed; and may be re-transformed, in another organism which supplies the necessary conditions. Thought may be restored. We have now reached, from a purely physiological standpoint, a position which I desired to reach before I advance the final part of the theory--which may at first sight appear somewhat fantastic. But telepathy itself is fantastic; and yet, being a fact, it must be accounted for somehow, or left altogether unexplained.