518 



BLOOD. 



Animal virus is, on the other hand, never medi- 

 cinal ; and no active animal substance can be em- 

 ployed in the cure of disease, even in the smallest 

 doses. Animal substances are however much more 

 easily assimilated than vegetable ones; and therefore 

 they can be advantageously employed in regimen, 

 and also mechanically in blunting the acridity of other 

 substances. But wherever an animal substance acts 

 upon the body in any more vigorous manner than 

 that of relieving some of the working structures, or 

 of shielding them from the action of some other 

 deleterious substance, it always acts as a systematic 

 poison. Farther, where any part of the body is de- 

 stroyed by the action of a distinct animal virus, whe- 

 ther that virus is one of inoculation, or of a disease 

 originating in the system, the part so destroyed is 

 never reproduced ; and even a wound which heals 

 by inflammation and granulation, and not by the first 

 intention, always leaves a scar. The case of some 

 putrid diseases attacking the animal system only 

 once, and being mitigated by inoculation, or pre- 

 vented by inoculation with the virus of another 

 disease, as in the prevention of human variola by 

 vaccination, whilst the body, in other cases, remains 

 as subject to a second attack of the disease as it was 

 to the first one, is an anomaly which we arc not very 

 able to explain, and which belongs to the medical 

 rather than the physiological consideration of the 

 animal economy. But the effects of those diseases 

 of inoculation, whether with virus obtained from 

 the same or a different species of animal, have the 

 same effects, where they destroy ever so small a por- 

 tion by suppuration. The scar which they leave is 

 never like the scar of a common wound, or that pro- 

 duced by the application of nitrate of silver or any 

 other caustic. Even in the case of vaccination, which 

 may be considered as the most simple of the whole, 

 if the scar which is left be smooth, like that from a 

 common wound or other topical injury by which the 

 system is not affected, the certain conclusion is that 

 the operation has failed, and must be repeated ; and 

 the honeycombed appearance of the scar, as if part 

 of the substance were eaten away, is the best, and, 

 after the inflammation is gone, almost the only cer- 

 tain evidence which we have of the success of the 

 operation. 



To those who are not much in the habit of reflecting 

 upon such subjects, it may seem that these observa- 

 tions, or the points to which they are directed, have 

 little to do with the popular history of animated 

 nature. But so far is this from being the case, that it 

 is for want of attention to those general means of 

 distinguishing the several kingdoms of nature from 

 each other, and of knowing arid describing each by 

 something more profound and permanent than mere 

 external appearances, that people in general take 

 much less interest in the study of nature, and derive 

 much less pleasure, and even profit, from it, than it 

 is calculated to afford ; and also, that those who, with 

 but little of the general principles of philosophy, and 

 consequently small capacity for comprehending the 

 action of general principles, drudge at the details of 

 some one department, till they become technical 

 adepts therein, and obtain such renown as this minor 

 species of learning is calculated to win, sometimes 

 jumble together the primary distinctions of kingdom 

 from kingdom, vitiate the whole subject to the igno- 

 rant, and make themselves most lamentably ridiculous 

 in the eyes of the few who are better informed. 



The action of mineral upon mineral, vegetable 

 upon vegetable, and animal upon animal, may in so 

 far help us to the knowledge of each in itself; but we 

 can sec the limits of each, and understand their 

 operations fully, only by attending to their action upon 

 each other. Now, if the preceding sentences of this 

 article have been read with even a moderate degree 

 of attention, it will be seen that, when we take the 

 action of each of the three upon the animal system, 

 in those cases in which that system itself is most 

 exclusively passive, it follows that, on this account, 

 the nature of the one which is active can be hot 

 ascertained. But, the only cases in which the animal 

 structure is passive to the action of minerals and 

 vegetables, are those in which these act as poisons, 

 and a very little reflection will show that such must 

 be the fact. A mineral acts only as matter a vege- 

 table only as organised or growing matter, which, 

 when it ceases to add to its volume in some way or 

 other, ceases to perform the functions of an organised 

 body but in the animal there is a distinct power, 

 apart from growth or addition of substance, which, 

 among its other functions, renovates or replaces the 

 old matter, which has become unfit for its economv, 

 by new matter obtained through assimilation ; and 

 while the animal continues capable of effecting this 

 renewal it lives, even though the body should he 

 gradually diminishing in volume, as is the case in the 

 decrepitude of man, and of some other animals, when 

 allowed to perish by natural decay. There is nothing 

 similar to this in the other kingdoms of nature. When 

 a mineral diminishes in size, it is by decomposition, 

 or by a closer union of the parts ; and though there 

 are apparent decreases in the volumes of vegetables, 

 these take place only when the proper vegetable 

 action ceases. When the heart, or oldest part of ;ui 

 aged tree, decays, the portions which remain alive 

 make their seasonal additions of wood in the same 

 manner, although not always to the same extent, as if 

 the whole tree were in action. So also, when trie 

 bleak winds appear to "eat the grass off the fields," 

 it is no more than a temporary fainting of the plant, 

 so to speak, which, if carried beyond a certain limit, 

 would destroy its action altogether. 



Thus, if we would characterise and distinguish the 

 three kingdoms of nature by their actions, which are, 

 for many reasons, the best means for such a purpose, 

 we must say that the vegetable is more active than 

 the mineral, and the animal more active than the 

 vegetable ; and therefore, when the action between 

 one of one kingdom and one of another is neutral, 

 that of the more active must so far predominate over 

 that of the less, as to give its own character both to 

 the mode of action and to the result. The victory, 

 so to speak, is so decidedly on the part of the more 

 energetic of the two, that it may be said, and in 

 common language it is said, to use the other. 



We have seen that a mineral acts upon the animal 

 body as if that also were a mineral ; and though we 

 have but little knowledge of the mode in which 

 vegetables act upon each other, yet they exert an 

 action upon the animal system so different from that 

 of poisonous minerals and animal virus of whatever 

 kind, that it may be considered peculiar and charac- 

 teristic. Even in the case of those " tree-nettles," 

 and other stinging plants, the action of which upon 

 one part of the body is followed by a rash or a 

 swelling of other parts, or even of the whole, the 

 effect appears to be secondary, more confined to the 



