PROFESSOR S1MONDS’ LECTURE. 515 
bodies were of greater specific gravity than the other parts of the 
blood, which was shewn by the fact, that when the coagulation of 
the blood was delayed, they settled to the bottom of the vessel. 
They were intimately connected with the health, strength, and 
vigour of an animal; for they were found to exist in a less pro¬ 
portion in the blood of an animal in ill health than in that of a 
robust one. The blood of a lean animal was also said to contain 
a larger quantity than that of a fat one. They were important 
also for another reason ; animals, as he had already stated, pos¬ 
sessed a power of keeping up a heat independent of the atmosphere, 
which was called animal heat, and it might be said that this pro¬ 
perty was in part owing to these bodies. 
The blood on entering the lungs became impregnated with the 
oxygen of the air which we breathed, and the oxygen supplying 
the place of the carbonic acid gas, caused the colour of the fluid to 
be changed. The Lecturer pointed out the mode in which the 
blood passed into the heart, and from thence into the arteries, by 
reference to a coloured drawing. The change which the blood 
underwent in its passage through the system was very important, 
as it then parted with its superabundance of oxygen by its union 
with the carbon, and thereby heat was produced. The carbonic 
acid thus formed, was got rid of during the process of respiration. 
Most of them were aware that chalk was a carbonate of lime, and 
they knew that carbonate of lime was not very soluble in w ater. 
The Lecturer exhibited some transparent lime water in a glass 
vessel, and by means of a tube he blew’ into it, when it was found 
that by mixing with the expired air from the lungs it became 
opaque. This experiment shewed that we had carbonic acid gas 
eliminated from the lungs in the act of respiration, and that this 
united with the lime in the water and formed it into a carbonate of 
lime. It was necessary that he should dwell briefly upon this 
part of the subject, because it had at one time been supposed that 
the carbonic acid gas exhaled from the lungs was formed by the 
oxygen breathed into the lungs uniting with the carbon of the 
blood in those organs; but this had been shewn to be incorrect, an 
interchange, but not a union of the two gases he had named, alone 
took place. The Lecturer then demonstrated the change which was 
produced in the blood upon its entering the lungs and becoming 
impregnated with oxygen, by pouring some oxygen upon a small 
quantity of black blood contained in a bottle. Immediately the 
blood assumed a bright red colour. The circulation through the 
lungs, he observed, was the great cause of the arterial change in the 
blood, while its passage through the capillaries of the system was 
the cause of its undergoing what was called the venous change. 
Many functions of the animal system might be stopped for a con¬ 
siderable time, but not that of respiration. This could only be 
