106 J. LeConte—Glycogenic function of the Liver. 
then by oxidation into CO, and H,O and eliminated by the 
lungs. The nitrogenous residuum if it is not at first urea is at 
least easily changed into urea and eliminated by the kidneys. 
We see then the close relation between the functions of the 
liver and kidneys. Now in going down the animal scale, we 
find in many cases, as for example in insects, that the same 
organ performs both functions. In the process of evolution urea 
was at first formed and excreted at once by the same organ. 
Afterwards these two processes were differentiated. 
7. We have already stated that Foster found a large percent- 
age of glycogen in the tissues of entozoa.* He asks, “ Of what 
use is this glycogen?” and answers, “ No respiratory use” is 
possible, for “having a constant temperature secured to them” 
by the body of their host, “they are the very last creatures to 
need respiratory or calorifacient material.” He, therefore, 
inclines to the view of Pavy, that glycogen is not respiratory 
material at all, but material on its way to become fibrin. On 
the contrary, we, for our part, see in this observation of the 
presence of stored amyloid in an animal not needing any inter- 
often or too strongly enforced that the prime object of com- 
bustion in the animal machine, as in the steam engine, is not 
heat-making but force-making. Heat is only a concomitant, often 
useful, but sometimes useless and even distressing. Careful 
experiments have over and over proved this; the doctrine of 
conservation of force absolutely requires it; and yet pbysiolo- 
gists still go on serenely talking of respiratory food as only heat- 
making, as if vital force were something wholly unrelated to 
other forces of nature and therefore requiring no explanation at 
all. e vital force created by combustion ma 
largely in mechanical power, as in the higher animals, or almost 
wholly in the vegetative functions of digestion, assimilation, 
secretion, &c., as in the more sluggish lower animals suc 
many mollusea and entozoa. 
Postseript.—Since finishing this article in April last, I have 
read with deep interest a very remarkable paper by Professor 
é * Proc. Roy. Soc., xiv, 543. 
