Annual Address by the President. 
7 
the outer layer (ectoderm) serving as a protective, tactile, and offensive 
covering, the inner layer as a digestive covering, while the middle layer 
is contractile to enable the animal to change its position for various 
purposes. These three primitive layers are adequate for all needs in 
the hydra., but more highly developed animals have modified them enor- 
mously to meet the needs of their particular environment, until we have 
most complex organs, resulting from these modifications. 
Yet, however highly specialized an organ becomes, it is alwnys more 
or less dependent on the other organs of the body for its proper work- 
ing. With some organs the connections may be apparently of the slen- 
derest, yet there is always some condition that will call for the help 
of an apparently useless organ. Physiological interdependence is the 
mainstay of life, without which chaos and dissolution would speedily 
result. 
It is a remarkable feature of animal life that, even where organs 
differ materially in anatomical structure, as, for example, in the gills 
of fishes, and the lungs of mammals, the retention of function is most 
tenacious. And even in animals of the same species (as in the alimen- 
tary canal of mammals) where great anatomical differences are seen, 
physiological function is retained with the greatest tenacity in corre- 
sponding parts. 
A moment’s thought will convince that, this retention of function 
was necessary for the preservation of life. For during the course of 
development, the changes in the anatomical structures of an organ 
could occur with impunity as long as the physiological function re- 
mained the same. But, if a coincident marked' and sudden change of 
physiological function became necessary, the other dependent organs 
would have been unable to respond, and death would have resulted. 
Under ordinary circumstances, then, the correlation of the physio- 
logical activities of the separate organs of the body is perfectly bal- 
anced. Each organ is capable of performing a. certain amount of work, 
and the assistance rendered by the other organs is proportional. Yet, 
under abnormal stimulation, each particular physiological activity is 
capable of being increased considerably until a point is reached, which 
has at times been designated as the breaking strain. This condition of 
excessive activity can only be produced by drawing on the physiological 
reserve of the tissues. In conditions of health every organ possesses 
considerable reserve. Ocular manifestation is present in the case of 
muscular contraction, where under great strain or intense excitement 
muscular contraction is possible to limits previously undreamed of. 
Pathologically, it is observed in all the tissues of the body, including 
the secreting glands. In vavular heart disease, it is in the early stages, 
the means by which the organ succeeds in propelling the necessary 
