ENDOCRINE ARITHMETIC 



figure, the actual weight of one molecule is 5.2 x 10"" gram. 

 Dividing this weight into the weight of the daily output of 

 one cell, we find that one cell produces about 1.3 x lO"-^ or 

 1,300,000,000,000 molecules, i.e. more than a thousand billion 

 molecules of secretion produced in one day by one cell. 



For comparison, it may be noted that in one cubic centi- 

 meter (about 1/3 of a thimbleful) of air there are about 10" 

 molecules. 



What has just been presented is to the best of my knowledge 

 the first attempt to calculate the actual output of a single 

 secretory cell in any organ. It is, of course, no more than a 

 first approximation to the truth. Yet such conjectures as 

 this, improved and extended beyond the present powers of 

 science, are going to lead us some day to the innermost secrets 

 of cellular life. Perhaps the reader begins to be confused by 

 all this reckoning of enormous numbers of very small things. 

 Perhaps, on the other hand, he has acquired an awesome sense 

 of the complexity of the cells, each one of them an island uni- 

 verse, a frail microscopic enclosure within which arise whirl- 

 ing billions of molecules, themselves in turn complex frame- 

 works of latticed atoms. Upon the correct behavior of these 

 fantastic congeries of particles in the corpus luteum each 

 one of us depended for life itself when we were embryos ; so 

 did all our mammalian ancestors and so will our descendants 

 forever. 



QUANTITATIVE ASPECTS OF THE RECEPTOR ORGAN 

 We can get a further glimpse of the workings of the corpus 

 luteum by doing a little figuring about the receptor organ, 

 that is to say the uterus, which receives the progesterone and 

 is affected by it. 



As we have seen (Chapter V) the corpus luteum acts upon 

 the epithelial cells which cover the inner surface of the uterus 

 and dip down to form the uterine glands. It is the growth and 

 multiplication of these cells which constitute the progesta- 



{ 187 ) 



