THE HORMONES IN HUMAN REPRODUCTION 



of menstruation and for threatened abortion have seldom 

 administered more than 2 mg. per day. If (as seems credible) 

 beneficial results have been obtained with this and even smaller 

 dosage, we must suppose that clinical benefit may require only 

 the redressing of a slightly disordered balance. Our calcula- 

 tions make it clear, however, that larger doses, of the order 

 of 5 mg. or more, will have to be given thorough trial before 

 the medical possibilities of this hormone are fully understood. 



6. What is the progesterone output of a single cell? Re- 

 turning to the rabbit's corpus luteum, it is possible to calcu- 

 late approximately the output of a single cell. 



The averages of a number of measurements of the diameters 

 of individual corpus luteum cells were 0.028 x 0.028 x 0.036 

 mm., giving for the cell a calculated volume of 0.000015 cu. 

 mm. Dividing this into the volume of the whole corpus luteum 

 we get 217,000, and making due allowance for space occupied 

 by the blood vessels we arrive at an estimate of 180,000 

 endocrine cells in one corpus luteum of the rabbit. 



Since 180,000 cells produce 0.13 mg. progesterone per day, 

 the daily output of otie cell is about 0.0000007 mg. 



The figure at first sight seems very small, but when the 

 number of molecules is considered the resultant expression 

 looks like the astronomer's rather than the biologist's quan- 

 tities. We get the number of molecules made by a single cell, 

 by the following calculation. We ascertain the molecular 

 weight of progesterone by adding the atomic weights of the 

 elements it is made of, namely 21 atoms of carbon, 30 of 

 hydrogen, and 2 of oxygen. The sum is 314. This is the rela- 

 tive weight in comparison with the atomic weight of oxygen 

 taken as 16. Applying Avogadro's law we know that 6 x 10^' 

 molecules^ weigh 314 grams. Dividing the latter by the former 



1 In dealing with very large numbers and very small decimal fractions 

 it is convenient to avoid writing dozens of ciphers by using exponents. 

 Thus 100 is 102 and .01 is 10-2. 600 is 6 x 102. The figure cited above, 

 6 X 1028, when written in full is 6 followed by 23 zeros, or six hundred 

 thousand billion billions. 



{ 186 } 



