ON GENERATION. 433 



who are agitated to such a degree by violent passion, that they 

 feel no pain, and pay no regard to the impressions made on 

 their senses, so must we believe it to be with this sense, which 

 we therefore distinguish from the proper animal sense. Now 

 such a sense do we observe in zoophytes or plant-animals, in 

 sponges, the sensitive plant, &c. 



Wherefore, as many animals are endowed with both sense 

 and motion without having a common sensorium or brain, such 

 as earthworms, caterpillars of various kinds, chrysalides, &c., 

 so also do certain natural actions take place in the embryo 

 and even in ourselves without the agency of the brain, and a 

 certain sensation takes place without consciousness. And as 

 medical writers teach that the natural differ from the animal 

 actions, so by parity of reason does the natural sense of touch 

 differ from the animal sense of touch, it constitutes, in a word, 

 another species of touch ; and whilst the one is communicated 

 to the common sensorium, the other is not so communicated. 



Further, it is one thing for a muscle to be contracted and 

 moved, and another for it by regulated contractions and relax- 

 ations to perform any movement, such as progression or prehen- 

 sion. The muscles or organs of motion, when affected with 

 spasms or convulsions from an irritating cause, are assuredly 

 moved no otherwise than the decapitated cock or hen, which is 

 agitated with many convulsive movements of its legs and wings, 

 but all confused and without a purpose, because the controlling 

 power of the brain has been taken away : common sensation 

 has disappeared, under the controlling influence of which these 

 motions were formerly coordinated to progression by walking 

 or to flight. 



We therefore conceive the fact to be that all the natu- 

 ral motions proceed from the power of the heart, and depend 

 on it ; the spontaneous motions, however, and those that com- 

 plete any motion which physicians entitle an animal motion, 

 cannot be performed without the controlling influence of the 

 brain and common sensation. For inasmuch as by this com- 

 mon sensation we are conscious of our perceptions, so also are 

 we conscious that we move, and this whether the motion be 

 regular or otherwise. 



We have an excellent example of both of these kinds of 

 motion in respiration. For the lungs, like the heart, are con- 



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