Sentence:  There are no reasons for supposing that any of the residual atmospheric oxygen is immediately combined with fixed or <WSD>nascent</WSD> hydrogen, or hydrocarbonate, in the venous blood at 98°, by slow combustion, and consequently none for supposing that water is immediately formed in respiration. 
Meaning of the word marked with <WSD> tags:  Of the state of an element at the time it is being generated from some compound or transitioning from one state to another; Newly released from a compound (especially hydrogen and oxygen) by a chemical reaction or electrolysis and possessing heightened reactivity; Newly synthesized (especially protein or RNA) by translation or transcription.