28 Additional Notes. 



seems to be no obstacle to the growth of aquatic animals; as by means 

 of the air-bladder, they can make their specific gravity the same as 

 that of the water in which they swim. And the moisture of the 

 element seems well adapted to counteract the rigidity of their fibres; 

 and as their exertions in locomotion, and the pressure of some parts 

 on others, are so much less than in the bodies of land animals. 



2. But as all excessive stimuli exhaust the sensorial power, and 

 render the system less excitable for a time till the quantity of sen- 

 sorial power is restored by sleep, or by the diminution or absence of 

 stimulus; which is seen by the weakness of inebriates for a day at 

 least after intoxication. And as the frequent repetition of this great 

 and unnatural stimulus of fermented liquors produces a permanent 

 debility, or disobedience of the system to the usual and natural kinds 

 and quantities of stimulus, as occurs in those who have long been 

 addicted to the ingurgitation of fermented liquors. 



And as, secondly, the too great deficiency of the quantity of 

 natural stimuli, as of food, and warmth, or of fresh air, produces also 

 diseases; as is often seen in the children of the poor in large towns, 

 who become scrofulous from want of due nourishment, and from 

 cold, damp, unairy lodgings. 



The great and principal means to prevent the approach of old age 

 and death, must consist in the due management of the quantity of 

 every kind of stimulus, but particularly of that from objects external 

 to the moving organ; Avhich may excite into action too great or too 

 small a quantity of the sensorial power of irritation, which principally 

 actuates the vital organs. Whence the use of much wine, or opium, 

 or spice, or of much salt, by their unnatural stimulus induces conse- 

 quent debility, and shortens life, on the one hand, by the exhaustion 

 of sensorial power; so on the other hand, the want of heat, food, and 

 fresh air, induces debility from defect of stimulus, and a consequent 

 accumulation of sensorial power, and a general debility of the system. 

 Whence arise the pains of cold and hunger, and those which are 

 called nervous; and which are the cause of hysteric, epileptic, and 

 perhaps of asthmatic paroxysms, and of the cold fits of fever. , 



3. Though all excesses of increase and decrease of stimulus should 

 be avoided, yet a certain variation of stimulus seems to prolong the 



