M A M M A L I A. 



117 



act is completed, tlie resulting substance is in itself as 

 passive as any of the parts of which it is composed. 

 It' we expose it to the air and the weather, to which 

 ull mammalia are more or less exposed, otherwise 

 they cannot perform their functions if we expose 

 it to these, their effects upon it is in all cases a de- 

 composing' or otherwise destructive one. There is 

 no principle of reproduction, no faculty of growth, 

 and no means of preservation in the inorganic or 

 dead substance. It, is perfectly passive to those phy- 

 sical laws which it is the province of natural philoso- 

 phy and chemistry to discover ; and were we ac- 

 quainted with the whole of those laws, we should 

 be intimately acquainted with the nature of every 

 organic substance, and could foretell the exact change 

 which under any given circumstances it would undergo, 

 with the same certainty as we can predict that tire 

 will burn dry wood, lead melt at a certain degree of 

 heat, and water crystallise into ice at a certain degree 

 of cold. 



In these inorganic or dead matters there is, there- 

 fore, strictly speaking, no physiology ; the individuals 

 or the kinds have no story to tell, for the whole of 

 their story is told in the physical laws of matter, and, 

 for the sake of illustration, it may be said that those 

 laws are inexorable despots to whom all the species 

 of inorganic matter yield the most implicit obedience. 



When however, we come to animals, and especially 

 to the mammalia, which are, as we have said, the 

 most typical animals, we find the case very different. 

 Tne physical laws of matter, taken generally, will 

 not only not explain their phenomena, but these phe- 

 nomena are dis-played in spite of the physical laws of 

 matter, and, iu opposition to them, by the triumph of 

 a greater power over them as it were. This is true 

 of the very materials of the animal body. The ani- 

 mal, or the principle of animal life that unseen j 

 power which we cannot describe except through the 

 medium of its phenomena cannot change the phy- 

 sical nature of any one substance, considered as a 

 simple substance, which enters into its composition. 

 Carbon, for instance, is exactly the same substance ( 

 in the body of a living animal as it is in a diamond, 

 in the charcoal of burnt wood, or in any mineral 

 carbonate, or compound of a carbonate. The oxy- i 

 gen and the hydrogen which exist in the structures 

 of an animal are also exactly the same as they exist 

 in water, or in any oxide or any hydrate whatever. 

 The same may be said of the nitrogen, and of all 

 the other elements which enter into the composi- : 

 tion of the animal body. And, as the action of the 

 animal has no power of changing the nature of any 

 one elementary substance, so it has not the power 

 either of producing or of finally destroying 1 any one 

 elementary matter ; so that, when an animal of the 

 largest size, the most active character, and the longest 

 life, ceases to exist, it leaves the quantity of matter, 

 and the proportions of those kinds of matter which 

 we call elementary, in precisely the same state that 

 they were at the dawn of its first rudimental existence. 



But though this is unquestionably true, and though 

 il is a truth necessary to a proper understanding of 

 the first and simplest principles in animal physiology 

 the principle upon which all our knowledge of a 

 subject so difficult and so apt to tempt us astray must 

 be grounded yet we must be careful as to what we , 

 understand by elementary matter of whatever kind. ! 

 For our purpose it is not necessary to inquire how 

 rnany kinds of elementary matter there are, or whether 



any one of those substances which the art of the 

 chemist has not hitherto been able to resolve into 

 parts, differing in their qualities from each other, is 

 or is not a simple element, and absolutely indecom- 

 posable. The practice belongs to the chemist, and is 

 in itself a physical maiterand not a physiological one ; 

 and being a physical matter, information concerning 

 it must be sought in those physical laws of matter 

 which, as we have said, are opposed and overcome 

 by the law c,f life in the individual animal as long as 

 its life continues. The principle is all that the phy- 

 siologist is concerned with ; but it is especially neces- 

 sary lliat his knowledge of this should be clear and 

 distinct, because the common loose expressions about 

 animal matter and vegetable matter, and matter which 

 is neither vegetable nor animal ; and also the distinc- 

 tive names given to imaginary kinds of animal matter, 

 such as the matter of bones, the matter of mem- 

 branes, the matter oi blood, the mutter of nerves, and 

 an endless variety of others, are !=ure to mislead us if 

 we do not clearly understand that they are simply 

 conventional expressions. 



When we speak of substantive matter as existent, 

 and obedient to the laws of matter and nothing more, 

 then there can be no such thing as animal matter, 

 because there must be something in addition both to 

 those laws and to the matter befoie there can be the 

 smallest part of the very smallest animal. When, 

 too, we speak of the different kinds of animal matter, 

 of those above alluded to, or others according to the 

 stiucture to which we refer, we do not mean different 

 kinds of substantive existence as merely matter, and 

 under the physical laws of matter and nothing more. 

 The real meaning of such expressions is, that each of 

 the compounds to whicli we allude is the result of 

 some degree or mode of animal action, wherein the 

 laws of mere matter have been subdued and suspended 

 for a time. 



In the general expression, " animal matter," our 

 real meaning, when we have any meaning at all (for 

 we are very apt to use such words without meaning), 

 is that this matter displays the result of the action of 

 animal life ; and when we speak of a particular kind 

 of animal matter, as, for instance, of the matter of 

 bones, all that we mean is, that a par.icular kind or 

 modification of the action of animal life is displayed 

 in the matter of which we speak. 



Even the words, " action of animal life," though 

 we cannot well refrain from us'ug them upon some oc- 

 casions, inasmuch as the lile of one animal displays 

 many species of action, are not altogether free from 

 objection. Our conceptions of life i.i animds. though 

 different in their subject, are similar in their nature 

 to our conceptions ot mind in man : we know nothing 

 of the essence either of the one or the other, but 

 merely their successive states; and tiiat which we 

 call the life of an animal, whatever it may be to our 

 thoughts, is nothing to our observation but the suc- 

 cession of actions which that animal performs. Some 

 of those actions are, however, so very different in their 

 nature from any action which we can attribute to mind, 

 as a thinking principle, that we naturally make a very 

 broad and clear distinction between the two. Mind is 

 capable of knowing matter, and turning its experimental 

 knowledge to account, whether sensation be imme- 

 diately concerned in this application of experience or 

 not; but mind is not capable of acting upon matter 

 so as to counteract or suspend any of those laws 

 which belong to matter. Il is emphatically said in 



