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SECTION III. 



RELATIONS OF BLOOD, AND ITS PRODUCTS, IN ITS VESSELS, 

 AND IN THE SEVERAL PLACES OF ITS DISTRIBUTION. 



CHAP. I. Formation of Blood. 



1. BLOOD is a conversion of chyle, or another change 

 in the preparation of that fluid furnished originally by food, and 

 traced through the processes of digestion, &c. We have found it 

 no difficult matter to specify the seats of certain conversions which 

 take place in the alimentary canal: it \vill not be found so easy to 

 assign the seat of conversion of lacteal chyle into blood; this, 

 however, is our present business. 



2. To pursue the question analytically, according to rules of 

 causation, would embrace an investigation with respect to the follow- 

 ing objects: 1st, it is to be determined whether blood has proper- 

 ties communicated to it, which properties are not possessed by 

 chyle; or, 2nd, whether chyle is made blood by a separation or 

 abstraction of some of its properties; 3rd, whether these modes 

 of causation both take place; and, 4th, what are those properties 

 which constitute the difference, whether foreign ones superadded 

 to chyle, or deficient ones abstracted from chyle, and by such ab- 

 straction admitting the condition of bloodl 5th, is blood made by 

 a single conversion of chyle in the sanguiferous system, or many 

 conversions? if the latter, the comparative changes are to be in- 

 vestigated with the above objects and the properties engaged, 

 specified ; 6th, the causation is to be proved by the analytical and 

 synthetical tests ; 7th, the seats of individual conversions or changes, 

 with the history belonging to each, are to be respectively developed 

 and assigned. An investigation, according to this method and 

 with these views, is to be hoped for in the progress of science : it 



