ORGANIC REMEDIAL AGENTS 



55 



77. We know for certain that the globules 

 of the venous blood, when they come in con- 

 tact with air in the lungs, change their co- 

 lour, and that this change of colour is ac- 

 companied by an absorption of oxygen ; and 

 that all those constituents of the blood which 

 possess in any degree the power of combining 

 with oxygen, absorb it in the lungs, and be- 

 come saturated with it. Although in contact 

 with these other compounds, the globules, 

 when arterialized, retain their florid, red co- 

 lour in the most minute ramifications of the 

 arteries ; and we observe them to change their 

 colour, and to assume the dark red colour 

 which characterizes venous blood, only 

 during their passage through the capillaries. 

 From these facts we must conclude that the 

 constituents of arterial blood are altogether 

 destitute of the power to deprive the arte- 

 rialized globules of the oxygen which they 

 have absorbed from the air; and we can 

 draw no other conclusion from the change 

 of colour which occurs in the capillaries, 

 than that the arterialized globules, during 

 their passage through the capillaries, return 

 to the condition which characterized them 

 in venous blood; that consequently, they 

 give up the oxygen absorbed in the lungs, 

 and thus acquire the power of combining 

 with that element afresh. 



78. We find, therefore, in arterial blood, 

 albumen, which, like all the other consti- 

 tuents of that fluid, has become saturated 

 with cxygen in its passage through the 

 lungs, and oxygen gas, which is conveyed 

 to every particle in the body in chemical 

 combination with the globules of the blood. 

 As far as our observations extend (in the 

 developement of the chick during incuba- 

 tion,) all the conditions seem to be here 

 united which are necessary to the formation 

 of every kind of tissue ; while that portion 

 of oxygen which is not consumed in the 

 growth or reproduction of organs combines 

 with the substance of the living parts, and 

 produces, by its union with their elements, 

 the act of transformation which we have 

 called the change of matter. 



79. It is obvious, that all compounds, of 

 whatever kind, which are present in the 

 capillaries, whether separated there, or in- 

 troduced by endosmosis or imbibition, if not 

 altogether incapable of uniting with oxygen, 

 must, Avhen in contact with the arterialized 

 globules, the carriers of oxygen, be affected 

 exactly in the same way as the solids form- 

 ing part of living organs. These com- 

 pounds, or their elements, will enter into 

 combination with oxygen, and in this case 

 there will either be no change of matter, or 

 that change will exhibit itself in another 

 form, yielding products of a different kind. 



80. The conception, then, of a change in 

 the two qualities of the blood above alluded 

 to, by means of a foreign body contained in 

 the blood or introduced into the circulation 

 (a medicinal agent) presupposes two kinds 

 of operation. 



Assuming that the remedy cannot enter 



' into any such chemical union with the con- 

 stituents of the blood as puts an end to the 

 vital activity ; assuming, further, that it is 

 not in a condition of transformation capable 

 '.of being communicated to the constituents 

 ! of the blood or of the organs, and of con- 

 tinuing in them ; assuming, lastly, that it is 

 incapable, by its contact with the living 

 parts, of putting a stop to the change of 

 matter, the transformation of their elements ; 

 then, in order to discover the modus ope- 

 rand! of this class of medicinal agents, no- 

 thing is left but to conclude that their 

 elements take a share in the formation of 

 certain constituents of the living body, or 

 in the production of certain secretions. 



81. The vital process of secretion, in so 

 far as it is related to the chemical forces, has 

 been subjected to examination in the preced- 

 ing pages. In the carnivora we have rea- 

 son to believe, that without the addition of 

 any foreign matter in the food, the bile and 

 the constituents of the urine are formed in 

 those parts where the change of matter takes 

 place. In other classes of animals, on the 

 other hand, we may suppose that in the or- 

 gan of secretion itself, the secreted fluid is 

 produced from certain matters conveyed to 

 it ; in the herbivora, for example, the bile is 

 formed from the elements of starch along 

 with those of a nitrogenized product of the 

 metamorphosis of the tissues. But this sup- 

 position by no means excludes the opinion, 

 that in the carnivora the products of the me- 

 tamorphosed tissues are resolved into bile, 

 uric acid, or urea, only after reaching the 

 secreting organ; nor the opinion that the 

 elements of the non-azotized food, conveyed 

 directly by the circulation to every part of 

 the body, where change of matter is going 

 on, may there unite with the elements of the 

 metamorphosed tissues, to form the constitu- 

 ents of the bile and of the urine. 



82. If we now assume, that certain me- 

 dicinal agents may become constituents of 

 secretions, this can only occur in two ways. 

 Either they enter the circulation, and take a 

 direct share in the change of matter in so 

 far as the : r elements enter into the compo- 

 sition of 'the new products ; or they are con- 

 veyed to the organs of secretion, where they 

 exert an influence on the formation or on 

 the quality of a secretion by the addition of 

 their elements. 



In either case, they must lose in the or- 

 ganism their chemical character ; and we 

 know with sufficient certainty, that this clasg 

 of medicinal bodies disappear in the body 

 without leaving a trace. In fact, if we as- 

 cribe to them any effect, they cannot lose 

 their peculiar character by the action of the 

 stomach ; their disappearance, therefore, pre- 

 supposes that they have been applied to cer- 

 tain purposes, which cannot be imagined to 

 occur without a change in their composition. 



83. Now, however limited may be our 

 knowledge of the composition of the differ- 

 ent secretions, with the exception of the 



| bile, this much is certain, that all the secre- 



