BLOOD. 



his nostrums ever so baneful. This universal craving 

 might be, and no doubt was intended to be, one of 

 the great inlets of knowledge ; but unfortunately it is 

 just as greedy of error ; and hence, as is the case with 

 all those which, under proper regulation, are capable of 

 effecting much good, it is made the means of much evil. 



Nor is it easy to say whether the pretender, who 

 seeks merely that living which he is incapable of 

 obtaining by honest industry, or the man of science, 

 who seeks for fame in an honourable way, has done 

 the most mischief here. The latter of the two is 

 deeply learned in the laws of matter, and, like a pedant 

 who darkens language, naturally obscure enough, 

 by his constant efforts to show his learning, or a man 

 who has become so much inured to the technicalities 

 of his craft, that he speaks in an unknown tongue to 

 all who are unacquainted with the minutiae of that 

 craft he will be constantly introducing his mechanical 

 philosophy and hU chemistry, whether they are con- 

 sistent with the subject or not. 



Chemistry, in that form which admits of experiment, 

 and can be reduced to a system in the schools, cannot 

 .in any way help to explain one single function of a 

 living animal. Even in the formation of carbonic acid 

 in breathing, the result is a chemical result certainly, 

 at all events, it is a result which could be obtained by 

 means of a common chemical experiment, in other 

 words, a product similar to that which results from 

 the process of breathing could be obtained by other 

 means ; but the process is not the same, and we 

 dare not call that chemical ; it is similar with all 

 the operations which are carried on in the living 

 body ; in as far as matter is put in motion they are 

 mechanical, and in as far as they tend to decompose 

 any substance they are chemical ; but the energy by 

 which these are accomplished is neither the one nor 

 the other it is physiological, belongs to the living 

 state only, and when that state is at an end, it exists 

 no more, and leaves not upon matter any trace of its 

 existence. 



In what may be called corporeal physiology, to 

 distinguish it from the more subtle subject of the 

 physiology of thought, the consideration of the 

 blood is by far the most important one ; and there- 

 fore, if we are not strictly physiological in it, if 

 we call in the assistance of chemistry, or of any 

 thing foreign to the nature of living action, we lay 

 an unstable foundation, and the whole structure of our 

 future knowledge becomes of small value. In the 

 following remarks on the nature of the blood, we shall 

 therefore consider the physiological phenomena as 

 the foundation and principle of the whole, though we 

 may have occasion to advert to some of the chemical 

 ingredients of the blood in illustration, but only as 

 proofs that there is an action, not as explanations of 

 either the cause or the manner of that action. 



Blood, when immediately taken from the vessels of 

 a living animal of any of the more completely de- 

 veloped vertebrated classes, appears a homogeneous 

 fluid, of somewhat viscid consistency, rather heavier 

 than water, of a red colour, and of the temperature of 

 the body from which it is taken, in man this being 

 about 98 of the common thermometer. This, while 

 it retains its primary heat, may be considered as 

 living blood, or the nearest approach which direct 

 observation can make to it in the vessels of the 

 animal ; but whether it is exactly the same, we have 

 no means of ascertaining ; for blood is a fluid so 

 susceptible to action, and capable of being acted 



upon (or acting) in so many ways, that we can have 

 no positive knowledge of the effect which the contact 

 of the atmosphere, however momentary, or the mere 

 taking of it out of the circulation, nay, the mere mo- 

 mentary stoppage of that circulation, may have upon it. 



This consideration tends very much to paralyse, at 

 the outset, all our inferences from what we can dis- 

 cover of the blood when out of the system, of the 

 functions which it performs, and the manner in which 

 it performs them, when in the system. 



After blood has been tor some time out of the 

 vessels, it separates into two parts, the one a yellowish 

 fluid, called serum, and the other an accumulation of 

 red particles, called crassamentum, or clot, which floats 

 in the serum, and may be divided by a knife, which 

 the serum cannot be. The experiments on the subject 

 have not been made with sufficient precision, or 

 in sufficient number ; but it would seem that this 

 coagulation of the blood, or separation of the serum 

 from the clot, takes place soonest in the i)lood 

 of those animals which are the most perfectly de- 

 veloped in their organisation, and which have the 

 circulation most rapid ; but this is still too vague for 

 allowing any conclusion to be safely founded upon it. 



If, during the time that it is coagulating, the blood 

 be gently agitated or stirred, the clot acquires a 

 fibrous consistency, which, when closely examined, 

 has the appearance of a kind of net-work, or of short 

 feathery fibres, which take hold of each other in all 

 directions. If, instead of being gently stirred, the 

 blood is violently, or even briskly agitated, the clot 

 does not separate either in a uniform mass, as when 

 left still, or in a fibrous tissue, as when stirred or 

 agitated gently. 



It is obviously not the presence of atmospheric air 

 which produces this change in the consistency, and 

 apparently in the composition of blood, for, as has 

 been said, blood coagulates in the interior of the 

 body, sometimes extravasated, and sometimes in its 

 own vessels ; and it would seem that, in those cases, 

 it is the clot of the blood which remains, the serous 

 part being taken up by the absorbents. Hence it is 

 probable that, in all cases in which inflammation, sup- 

 puration, or gangrene follow upon the extravasation 

 of blood in the system, one of the causes, at least, is 

 the incapacity of the absorbents to take up the serum, 

 for in those portions which are found harmlessly 

 bedded in the substance of the body, it is the clot 

 only which is left. 



If the fibrous clot which is obtained by gentle 

 agitation of the blood be repeatedly washed in water, 

 the colouring matter is entirely removed, and the 

 fibres, or fibrin, as the substance is called, become 

 nearly colourless, and is tough and elastic. Fibrin, 

 in the same state of adhesion and elasticity, cannot 

 be obtained either from blood which is left at rest, or 

 from that which is subjected to violent agitation ; but 

 what correspondence there is between the degree of 

 agitation necessary to prevent the separation of the 

 fibrin, and the rate of healthy circulation in the 

 animal from which the blood is taken, has not been 

 ascertained by experience, though it is unquestionably 

 a point of very great importance, and the one, the 

 solution of which is most likely to throw light (if any 

 inquiry can throw light) upon the manner in which the 

 repairs of the different animal structures, or even their 

 formations at first, are elaborated from the blood. 



We have it established by direct observation, that, 

 where blood is allowed to remain still, or where the 



