188 ALLOTEOPISM OF OEGANIC BODIES. 



why was the zinc passive when alone, and why did it assume this activ- 

 ity when merely touched by another metal ? Does not all this serve to 

 show that substances may be, as it were, in a quiescent state, and on the 

 application of what may perhaps seem the most insignificant cause, may 

 suddenly assume activity, and forthwith satisfy their chemical affinities ? 

 There is nothing in the graduated oxidations going on in the system 

 more obscure or more unaccountable than the phenomena of a simple 

 Voltaic circle. Their effects are almost parallel. 



All elementary substances appear to have the quality of assuming active 

 Allotropism of and passive conditions. Carbon, moreover, presents many 

 bodies. intermediate forms. As diamond it is extremely incombus- 



tible, and is set on fire with difficulty even in oxygen gas ; as lampblack 

 it will kindle spontaneously. With these differences in its relations with 

 oxygen, it also exhibits great variations in its optical, calorific, mechan- 

 ical, and other properties. These transitions of state may be induced by 

 various causes, especially by the agency of what are called the impon- 

 derable principles, as by rise of temperature, and exposure to the sun- 

 light. Thus, in the case of chlorine, I have shown that, though it re- 

 fuses to combine with hydrogen so long as it is in the dark, an exposure 

 to indigo-colored light will cause it to unite with explosive energy with 

 that substance ; and these peculiarities are retained by bodies when 

 they go into union with each other. Thus there are two forms of phos- 

 phorus; the one active and shining in the dark, and therefore readily oxi- 

 dizable ; the other passive, not shining in the dark, and with therefore a 

 less affinity for oxygen ; and these severally give rise to two varieties 

 of phosphureted hydrogen, which, though having the same composition, 

 yet differ in thi's respect, that the one containing the active form of phos- 

 phorus is spontaneously combustible in the air, but the other, which con- 

 tains the passive form, is not spontaneously combustible. Phosphorus 

 is thrown from the active to the inactive state by mere exposure to the 

 more refrangible rays of the sun. 



The properties here spoken of have been designated by Berzelius as 

 Allotropism of ^ ie a ^otropism of bodies. I have endeavored to prove that 

 organized bod- allotropism is the true cause of many of the obscure facts 

 which we meet with in the animal mechanism ; for it is very 

 clear that something so modifies the relations of the tissues to oxygen 

 that they are not indiscriminately destroyed by it, but these parts yield 

 in a measured or regulated way ; and since, in inorganic substances, the 

 influence of the imponderables can compel the assumption of an active or 

 passive state, there is nothing contradictory in imputing to the nervous 

 system a similar power. 



In this manner we may therefore conclude that, so far as tissue de- 

 struction is concerned, the nervous system possesses a governing or con- 



