Lecture I ^ 



THE UNIQUE MAMMAL 



There are living today on the earth well over 5000 different 

 recognizable kinds of animals that have the habit in common of 

 getting their young started on their individual life journeys in 

 a strange way. The mothers elaborate in their own bodies a 

 fluid that is one of the most perfect all round foods known to 

 bio-chemistry and physiology. Furthermore these mothers have 

 their bodies so built as to provide a simple but extremely neat, 

 handy, and beautiful piece of machinery from which their off- 

 spring from the moment they begin their free life in the world 

 can get this almost perfect food with a minimum of effort j and 

 without the necessity for the exercise on their part of either 

 intelligence or cunning. It is in fact as easy for them to get this 

 nourishment as it is for them to beat their hearts or to breathe j 

 and, alas, sometimes much easier than it is for them to digest 

 the food after they have got their little paunches full of it. 



Because the mothers treat their young in this generous fashion 

 all these thousands of kinds of animals are called mammals. 

 Nearly all of them are distinguished from all other animals in 

 two further ways — one really important biologically and the 

 other merely odd. The first and important distinction is where 

 the mother again shines. She provides for the embryonic de- 

 velopment of her young within the superb physiological pro- 

 tection of her own body during the long period from the fer- 

 tilization of her eggs up to the time the offspring are ready to 

 be born. The machinery of this most perfectly regulated of 

 incubators is highly complicated — too much so to be gone into 



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