1004 EXPERIMENT STATION RECORD. 



The investigations with hens' and clucks' eggs incubated for differ- 

 ent j^eriods have given new evidence regarding the synthesis puri in 

 embryonic life, the fresh egg being practically free from puri. In the 

 case of the embryonic pig it was found that the developing muscle 

 tissue contained glycogen during embryonic life, Avhich during the 

 early stages of this period had a relatively greater digesting power 

 than that of the liver tissue ; while the embryo liver in the early stages 

 of development is entirely free from glycogen and only graduallj^ 

 acquires its characteristic digesting capacity. 



The influence of the nervous system in connection with the activi- 

 ties of the body has long been regarded as very important, but more 

 recent study indicates the action of another series of agents. These 

 are excitatory substances of chemical character, which act as a con- 

 necting or controlling mechanism in coordinating the activities of 

 various organs. 



We are accustomed, as Starling says, to regard each act in the life 

 of an animal as a link in a never-ending chain of adaptations to the 

 environment, each act being a complex of a number of mutually 

 adapted activities affecting very different parts of the body. This 

 united action of several different organs seems to call for the exist- 

 ence of some connecting or controlling agent. In many cases this is 

 represented by the nervous system, but in many others it now appears 

 to be effected by chemical means, which are present in the internal 

 nutrient fluid of organisms, and function not as foods in the ordinary 

 sense but as excitatory substances. 



For these chemical compounds, called " reizstoffe " by the Germans, 

 Starling suggests the name of " hormones." These bodies, it is 

 found, can be isolated and studied as to their nature and function, 

 and this has been done successfully in the case of certain of them. 

 They are believed to be nonassimilable and to yield no appreciable 

 amount of energy, but their importance depends on their dynamic 

 effects on the living cells. 



A striking illustration of this chemical stinudation is met Avith in 

 the alimentary tract. The secretion of digestive juices by organs 

 which are remote from each other and apparently without connection 

 is found to be brought about by definite substances for which the 

 name " secretins " has been proposed. It appears that after digestion 

 has begun b}?^ psychic stimulation the digestive processes are con- 

 tinued entirely by chemical stimulation, the stimulating material or 

 materials first formed passing into the blood and being carried to the 

 next set of organs which require stimulation in order to pour out the 

 digestive juice. 



This investigation represents an attempt to determine not merely 

 what the return will be from a certain feeding stuff', or how much 

 of it is digested, but the manner in which digestion takes place, the 



