406 - FRANK R, LILLIE 



tT\'ins to cattle. (5) We have shown that there is a firm basis 

 for the hormone theory in the known data concerning the time 

 of origin of interstitial tissue in the testis and in the ovary. 

 (6) We have also shown why the effect is limited to the female. 



V. THE EMBRYONIC AND ADULT ANATOMY OF THE FREE-MARTIN 



We can now proceed to a discussion of the anatomy of various 

 stages of the free-martin with a firm basis for interpretation of 

 the conditions. This will be considered under two heads, A. the 

 gross anatomy, B. the microscopic anatomy. The second sec- 

 tion has been worked up by Miss Catherine L. Chapin from my 

 material, and is published as a separate paper immediately 

 following this. 



The gross anatomy 



The mammalian embryo passes through a stage of complete 

 sexual indifference anatomically, in which all the organs of both 

 sexes are represented by embryonic rudiments in each individ- 

 ual; the anatomical sex differentiation that follows is due to 

 progi'essive development of certain parts and degeneration of 

 others in different Avays in the two sexes. This is such a com- 

 monplace in embryology that it seems unnecessary to describe 

 the anatomy of the indifferent stage. 



For comparison with the anatomy of the free-martins I have 

 introduced figures of the normal female reproductive system of 

 embryos 10.2 cm. long (fig. 6), 17 cm. long (fig. 9), 20 cm. long 

 (fig. 7) and 23.3 cm. long (fig. 8), and of the normal male repro- 

 ductive system of embryos 10.4 cm. long (fig. 10), 15.8 cm. long 

 (fig. 11), and 26 cm. long (fig. 12). The free-martins will be 

 described in the order from the youngest to the oldest. ' The 

 written descriptions are given very briefly, and the reader should 

 refer to the figures for details. The exact interpretation of the 

 ducts is often difficult or impossible on the gross anatomical 

 evidence alone; Miss Chapin's descriptions should be compared. 



1. Case 19. cf 8 cm.; ^ 7.5 cm. in length; figure 13, urino- 

 genital Septem of Female. X 4. (Cf. Miss Chapin's descrip- 

 tion of the histology of this specimen in the paper following.) 



