PLANTS AND ANIMALS. 
31 
that membrane, of modifying the impressions of sound by 
change of tension, was attempted to be supplied by strain¬ 
ing the muscles of the outward ear. “ The external ear,” 
we are told, “ had acquired a distinct motion upward and 
backward, which was observable whenever the patient 
listened to anything which he did not distinctly hear; 
when he was addressed in a whisper, the ear was seen im¬ 
mediately to move; when the tone of voice was louder, 
it then remained altogether motionless.” 
It appears probable, from both these cases, that a collate¬ 
ral, if not principal, use of the membrane, is to cover and 
protect the barrel of the ear which lies behind it. Both 
the patients suffered from cold: one, “ a great increase of 
deafness from catching cold;” the other, “ very considera¬ 
ble pain from exposure to a stream of cold air.” Bad ef¬ 
fects therefore followed from this cavity being left open to 
the external air; yet, had the Author of nature shut it up by 
any other cover, than what was capable, by its texture, of 
receiving vibrations from sound, and, by its connexion 
with the interior parts, of transmitting those vibrations to 
the brain, the use of the organ, so far as we can judge, 
must have been entirely obstructed. 
CHAPTER IV. 
OF THE SUCCESSION OF PLANTS AND ANIMALS. 
The generation of the animal no more accounts for the 
contrivance of the eye or ear, than, upon the supposition 
stated in a preceding chapter, the production of a watch 
by the motion and mechanism of a former watch, would 
account for the skill and intention evidenced in the watch 
so produced; than it would account for the disposition of 
the wheels, the catching of their teeth, the relation of the 
several parts of the works to one another, and to their com¬ 
mon end; for the suitableness of their forms and places to 
their offices, for their connexion, their operation, and the 
useful result of that operation. I do insist most strenu¬ 
ously upon the correctness of this comparison; that it 
holds as to every mode of specific propagation; and that 
whatever was true of the watch, under the hypothesis 
above mentioned, is true of plants and animals. 
I. To begin with the fructification of plants. Can it be 
doubted but that the seed contains a particular organiza* 
