184 The English School [lect. 



colour. He further saw that when the artificial respiration was 

 stopped, when no fresh air was driven into the lungs, when the 

 animal was suffocated, the blood in the pulmonary veins and in 

 the left side of the heart became dark and venous. He took 

 dark venous blood from the vena cava, and injected it artificially 

 through the lungs. He* found that so long as insufflation of 

 the lungs was kept up the blood ran out by the pulmonary 

 veins florid in colour, but ran out dark and unchanged if no 

 fresh air was driven in to the lungs. 



He concluded that the change in colour was due simply to 

 the blood being exposed in the lungs to air; and he was 

 confirmed in this conclusion by observing the fact that a clot 

 of dark venous blood soon becomes florid on the upper surface 

 where it is exposed to the air ; and that if the cake be turned 

 upside down the under dark surface also soon becomes florid. 



And he at once took the next step and drew the further 

 conclusion that the change in colour was due not to mere 

 exposure alone but to the blood taking up some of the air. 

 Arterial blood, according to him, differs from venous in that 

 it contains air; as the florid arterial blood passes from the 

 body air escapes from it and it becomes dark and venous; as 

 the dark venous blood passes through the pulmonary circulation 

 it takes up air again and once more becomes florid and arterial. 



It is this continual entrance of fresh air into the blood 

 which renders fresh air so necessary for the maintenance of 

 life. " Were it not for this we should breathe as well in the 

 " most filthy prison as among the most delightful pastures." 

 The same fresh air is as much needed for our breathing as 

 for the burning of a flame, " in fact where a fire burns readily, 

 " there can we easily breathe." 



Lower speaks only of air being taken up as air, and as we 

 have seen Borelli had also come to the conclusion tliat air is 

 taken up by the blood in the lungs ; but he writing towards the 

 end of the seventies might have been acquainted with Lower's 

 results. Neither one nor the other alludes to the possibility 

 of a part of the air only being taken. It was the common 

 opinion of the time and one which lasted for long afterwards 

 that air, the air of the atmosphere, was a single substance not 



