138 THE BIOLOGY OF BIRDS 



remarkable organ, partly nervous and partly glandular, which 

 hangs down from the floor of the optic thalami of the brain, 

 and arises in development as a downgrowth from the brain 

 meeting an upgrowth from the mouth, the two portions 

 entering into very intimate union. 



All these organs are secretory and all are ductless ; 

 they are known as organs of internal secretion or cndocrinal 

 glands. The fluid substances they produce are carried 

 away by the blood and distributed throughout the body, 

 having specific effects upon specific parts. There are 

 some other parts of the body which produce internal secre- 

 tions which the blood sweeps away. This is true, for 

 instance, of the reproductive organs (ovary and testis), 

 though their primary and chief function is, of course, to 

 make ova and spermatozoa. The exceedingly important 

 uses of the internal secretions must now be considered. 



There is undoubtedly a certain amount of competition 

 among the different parts of the body, but the larger fact 

 is their correlation. They seem to work into one another's 

 hands, as if they had, in St. Paul's words, " a common 

 concern for one another." This harmonious unification 

 is in great part due to the nervous system, which has what 

 one of the great neurologists calls an " integrative function." 

 The central government is made aware of the needs of the 

 outlying parts, and may supply these almost automatically, 

 reflexly, as we say. More than that, the remote parts and 

 the intricate recesses may be thrilled by or attuned to the 

 purpose and feeling of the central government. " An 

 artist to his finger-tips," we justly say. Another correlation 

 is effected by means of the blood, that common medium 

 from which every part derives sustenance and to which 

 every part makes contributions. Now it is to the general 

 idea of the blood as a correlating medium that there has 

 been added in the last thirty years or so a recognition of 

 the role of the ductless glands or " organs of internal 

 secretion." Apart from anticipatory glimpses by Claude 

 Bernard and others, it is to Brown-Sequard that credit is 

 due for first clearly discerning that a specific secretion may 



