MODERN CONCEPTION OF PROTOPLASM. 31 
He waste products which are formed as the ashes of 
life. 
There are indeed some organs which we have not 
mentioned, such as the spleen, which seems to be an area 
for the multiplication of red blood corpuscles (fishes, 
newts, embryo-mammals) or for the destruction of worn- 
out corpuscles (mammals), and the thyroid gland, which 
seems to have to do with keeping the blood at a certain 
standard of efficiency; but what we have said is perhaps 
enough to convey a general idea of the processes of life 
in a higher animal. 
In conclusion, it is perhaps useful to remark that whén in the 
course of further studies the student meets with organs which are called 
by the same name as those found in man or in Mammals, as, for 
example, the “‘liver” of the Molluscs, he must be careful not to 
suppose that the function of such a ‘‘ liver” is the same as in Mammals, 
for comparatively little investigation into the physiology of the lower 
types of animal life has as yet been made. At the same time, he must 
clearly recognise that the great internal activities are in a general way 
the same in all animals; thus respiration, whether accomplished by 
skin, or gills, or air-tubes, or lungs, by help of the red pigment (hzemo- 
globin) of the blood, or of some pigment which is not red, or occurring 
without the presence of any blood at all, always means that oxygen is 
absorbed almost like a kind of food by the tissues, and that the carbon 
dioxide which results from the oxidation of part of the material of the 
tissues is removed. 
MopERN CONCEPTION OF PROTOPLASM 
The activities of animals are ultimately due to physical 
and chemical changes associated with the living matter or 
protoplasm. This is a mere truism. We do not know 
the nature of this living matter; perhaps our most certain 
knowledge of it is, that in our brains its activity is 
associated with consciousness. 
When more is known in regard to the chemistry and 
physics of living matter, it may be possible to bring vital 
phenomena more into line with the changes which are 
observed in inorganic things. At present, however, it is 
idle to deny that vital phenomena are things apart. Not 
even the simplest of them can be explained in terms of 
chemistry and physics. Even the passage of digested food 
from the gut to the blood vessels is more than ordinary 
