1868. ] E15 
10. ZOOLOGY—ANIMAL PHYSIOLOGY AND 
MORPHOLOGY. 
PuystoLoey. 
Work and Food.—A new phase of this question has been brought 
about by the very valuable experiments of Dr. Parkes (of the 
Military Hospital and Medical School at Netley) on the Elimination 
of Nitrogen during rest, an account of which he has communicated 
to the Royal Society. We have in a previous Chronicle noticed the 
views and experiments of Fick, Wislicenus, Frankland, and the first 
series of Dr. Parkes’ researches.* Dr. Parkes has found that during 
a period of work a man excretes less nitrogen than during a period 
of rest—whether he feeds on nitrogenous food or carbonaceous only. 
He also finds that after nitrogenous food has been cut off from the 
system and again supplied, there is a retention of that nitrogen 
showing that it is needed to fill up some waste; also, that during 
the first rest after exercise, where nitrogenous food had not been cut 
off, there was an increase in the elimination of nitrogen. The ex- 
periments on which these statements are founded may be thoroughly 
trusted, and lead to important considerations, Dr. Parkes having 
experimented on two soldiers, and having every means of analysis 
at hand. It will be seen that they place the question in quite a new 
aspect, and no theory of the relation of food, muscle, and work can 
be now tenable which does not account for them. Dr. Parkes’ view 
is, that when a voluntary muscle is brought into action by the in- 
fluence of the will, it appropriates nitrogenous matter and grows; 
the stimulus onthe act of union gives rise to changes in the non- 
nitrogenous substances surrounding the ultimate elements of the 
muscular substance, which cause the conversion of heat into motion. 
The contraction continues until the effete products of these changes 
arrest it (as they have been shown to do by Ranke and others), a 
state of rest ensues, during which time the effete products are re- 
moved, the muscle loses nitrogen, and can again be called into action 
by its stimulus. Dr. Parkes does not believe in the efficiency of 
carbonaceous foods when alone, which recent experiments might seem 
to indicate. Fick and Wislicenus, he says, drew upon the store of 
nitrogenous matter in their system when they cut it off in their food, 
and he maintains that carbon foods can only be efficient in the pre- 
sence of nitrogenous matter also. When a muscle loses nitrogen, fat 
is probably formed, and thus a muscle, disintegrating during the 
period of rest, may form a store of fat in its texture, which may 
become efficient at the next addition of nitrogenous matter as a 
source of force. The argument as to the oxidation of nitrogenous 
matter beg insuflicient to account for work is true enough, but 
* See also Dr. Hinton’s paper in the July number. 
