BLOOD. 



521 



the subject of health and disease is an exceedingly 

 ample one. Still the blood may take up, either by 

 inoculation, by absorption, or by the common process 

 of assimilation or chylefaction, substances which ren- 

 der its action, upon the containing vessels and the 

 system generally, pernicious instead of wholesome ; 

 and in very many instances in which curative prepa- 

 rations are exhibited, they are understood to act upon 

 the system through the medium of the blood, which 

 is sometimes reached by the process of chylefaction, 

 sometimes by that of absorption, and sometimes again 

 by tension or by relaxation of the vessels, according to 

 circumstances. .These views of the subject and means 

 of acting upon the system belong to medicine rather 

 than to natural history, though some knowledge of 

 them is necessary for the prevention of mistakes and 

 errors in that science. 



Nature and Action of the Blood. In briefly glancing 

 at this part of the subject, it is not necessary to enter 

 into any investigation of the chemical nature and 

 composition of the blood, because the action of that 

 fluid upon the animal system is not chemical, that is, 

 it does not obey the same laws which are obeyed in 

 the chemical action of dead matter. Indeed, the 

 whole action of the animal system is in opposition to 

 these laws. The energy of life, though undefinable 

 in any other way than by its phenomena, is more 

 mighty than these laws, and holds them suspended as 

 long as the organisation of the individual is capable 

 of obeying the living impulse. When disease invades 

 and deranges the system, the natural or chemical 

 powers or properties of the component substances of 

 the organisation begin to operate, and the disease 

 takes more or less of a putrid type, so much so 

 that, in certain states of disease, it appears that the 

 matter given out by the affected body, even when in 

 the form of insensible perspiration, and not discernible 

 by any test, is capable of communicating the disease 

 to healthy bodies in that mysterious way which we 

 call infection. But it is not till the whole body has 

 ceased to live, and a time, longer or shorter accordin 

 to circumstances, has passed over it (always shorter 

 the more the disease has of a putrid type, and the 

 more energetic the action of nature around), that it 

 yields wholly to the laws of inorganic chemistry ol 

 that chemistry in which alone we can make experi- 

 ments, and in so far explain principles by means oi 

 these experiments. 



From these considerations, it is evident that, if we 

 attempt to apply our common chemistry to investigate 

 the composition of the blood, and thence venture to 

 give explanations of any of the functions of life, we 

 are in error ; because we are attempting to explain the 

 actions of the living body by means of agencies, the 

 suspension of which is involved in the very notion 

 anil definition of life, and which cannot, by possibility 

 be exerted upon any part of the body till life itself is 

 extinct. 



It is necessary for us to be constantly upon our 

 guard lest we should confound dead and living action 

 i use there is, not in the ignorant only, but in the 

 scientific, and indeed in them more than in the 

 ignorant, a constant tendency to this confusion. This 

 arises from the succession of fashions in philosophy 

 which follow the same law as fashions in commor 

 matters, but are far more inveterate, and we may add 

 far more mischievous, because they affect the whole 

 character of society, intellectual and moral, while thf 

 others, if they do this at all. do it only at second hand 



When the principles of mechanical jxhilosophy were 

 n their prime, and, as it were, held the whole field of 

 cience, it was the fashion to attempt the explanation 

 jf everything upon mechanical principles, and not 

 only the action of the living body, in all those 

 unctions which are necessary for the preservation of 

 he individual, but sensation and perception, and 

 even thought, were attempted to be explained on the 

 same laws which determine the motion of the planets 

 n their orbits, or the tidal motions of the ocean 

 waters. When chemical science, (the principles of 

 which being of a more complicated and less obvious 

 nature, necessarily came after those of mechanical 

 >hilosophy,) had made such advances as to take the 

 ead and become the fashion, the whole action of the 

 iving body was considered as chemical, and ex 

 jlainable by the laws of chemical attractions and 

 repulsions, with their attendant compositions and 

 decompositions. This was not, in an intellectual 

 point of view, carried so far as the other ; for no one 

 ever gravely supposed that sensation, far less thought, 

 was a result of chemical action, or ventured to re- 

 commend alembics and crucibles with sand-baths 

 and fires, as appropriate substitutes for the old and 

 vulgar process of thinking. They did not even 

 attempt, by chemical means, to give sight to the eye 

 or hearing to the ear, .as had been partially done by 

 the application of mechanical instruments, but in so 

 far as what may be called the proper functions of the 

 body, those which develope its organisation and pre- 

 serve it in a living and healthy state were concerned, 

 chemistry was the rule of action, and when the body 

 became diseased, chemistry was the grand means of 

 cure. It is true, that a mixer of medicines had been 

 called a" chemist" before this time ; but a chemist, in the 

 general sense of the trm, means one who is possessed 

 of, or who deals in secrets ; and in the composition 

 of medicines there are some real secrets, and many 

 more which belong to that class which are most safely 

 kept those in which there is nothing that can be 

 revealed. In addition to these two general modes of 

 endeavouring to explain the functions of the living 

 body by means of principles, the resistance of which 

 forms the best definition of life, there were always 

 minor modes of a transcendental nature (or which 

 could not be reduced to any principles) breaking in 

 still farther to confuse a subject which is certain at 

 all times to claim much attention, but which has at no 

 time been explained, or even clearly defined. 



Life, that which puts into action all the organs and 

 structures of the animal body, is so interesting in wild 

 nature, and so useful in domestication, is the portion 

 of creation which all are most desirous of understand- 

 ing ; and, whatever may have been the case with any 

 other subject, there is no human being, learned o"r 

 unlearned, that has not thought and speculated about 

 this one. 



" Who, to dumb forgetfulness a prey, 

 This pleasing anxious being e'er resigned ! " 



is true, not only when we consign to the earth the 

 mortal remains of those who have been dear to us, 

 but of our own living bodies, and of those of all the 

 creatures which live around us. Hence, be it as 

 crabbed or as absurd as it may, a book upon the 

 functions of life, and more especially one upon the 

 functions of human life, is sure to find readers, upon 

 the same principle that he who pretends loudly 

 enough to cure human disease is sure to find en- 

 couragement, be his knowledge ever so limited, and 



