320 Biology in America 



common reactions of higher animals. Can "memory images" 

 teach a bird liow to build its nest for the first time, or guide 

 the bees in the eonstruetiou of theii* wonderful condjs? Can 

 tlieir "oi-ientiug effect" explain the return to its nest of the 

 terns 'whieh AVatson carried from the Florida Keys to Cape 

 Ilatteras, a distance of 150 miles from their houu\ into a re- 

 gion never before visited by the birds? Possibly, although 

 it requires a mighty effort of the imagination to unite cause 

 and effect in this instance. But it is easy to find flaws in 

 any theory Avhieh boldly ventures into the comparatively 

 uncharted sea of animal reactions, and endeavors tliere to 

 lay down a course which we may in safety follow ; so let us 

 comfort ourselves with believing that "free will" has no 

 place in science, but is merely an expression of the "verbal- 

 ists," and tliat we simply "go where our legs carry us," a 

 theory which has at least the advantage of enabling us to 

 smile complacently, while ancient preachers hurl their an- 

 athemas at the damned. 



We have spoken above of certain substances secreted by 

 the animal body and known as hormones, which exercise a 

 determining influence in animal behavior. What are these 

 substances, how are they formed and what role do they play 

 in animal physiology? 



The recognition of the value of various organs in curing 

 disease goes back to the days of Hippocrates, the "father 

 of medicine," and since his time many such remedies have 

 been proposed. Thus the liver of the pigeon or the wolf were 

 used in cases of disease of the liver, the rabbit's brain was 

 given for tremors, and the lung of the fox for difficulty in 

 breathing. The testicles of the donkey or the stag were rec- 

 ommended by Pliny foi- the renovation of the debauchee, and 

 even today (castoreum) a preparation obtained from the 

 prei)utial glands of the beaver is sometimes employed for 

 colic, hysteria and other disorders. In more recent days the 

 French physiologist Claude Bernai'd advanced the view that 

 all tissues give some secretion to the blood, which is of use 

 in the nutrition of the body, and while our knowledge of 

 these substances is as yet very fragmentary, their great im- 

 portance in the life of the animal and their usefulness in the 

 treatment of various disorck'rs, are widely recognized. It is 

 known for example that diabetes, which is marked by the 

 presence of sugar in the urine, is not a kidney disorder, but 

 is due to improper actio]i of the pancreas, as a result of 

 which a specific secretion, passed by the latter into the blood 

 stream and functioning in sugar metabolism, is absent or re- 

 duced in amount. 



Imperfect development of the thyroid gland leads to the 



