64 B. F. KINGSBURY 



been devoted. The conclusions in favor of the 'interstitial gland' 

 interpretation have perhaps been largely based on the condi- 

 tions in the rabbit and bat. Only a few observations have, 

 therefore, been made as far as known to me on the lower orders 

 of mammals (marsupials and edentates) by Benthin ('11) and 

 Schaeffer ('11). Within the range of animal forms examined, 

 interstitial cells are present in very varying numbers. Thickly 

 massed in the rabbit, they are present in large amount in the 

 cat's ovary, scantily developed in the human ovary, they ap- 

 pear to be practically absent in certain other forms, such as the 

 pig, sheep, cow. In general, it would seem that they are abun- 

 dantly present in the small mammals examined and few or 

 absent in the larger mammals in the adult. 



The great variability in their development certainly calls for 

 careful consideration in drawing any general conclusions as to 

 their significance, as has been insisted upon by Friinkel ('05). 

 Furthermore, it would appear that the same variability is found 

 in the period of life at which the interstitial cells are present. 

 Upon this basis Aime divided the mammals into four groups: 

 (a) those in which the 'interstitial gland' occurs in fetal life 

 only (e.g., the horse); (b) those in which the 'interstitial gland' 

 is present only in postpartum (essentially, adult) life (Chiroptera, 

 Insectivora, rodents); (c) forms possessing no 'interstitial gland,' 

 wherein he included man, pig, sheep, goat, boar, dog; (d) mam- 

 mals in which an 'interstitial gland' occurs both antepartum and 

 postpartum, as an example of which group he gives the cat. It 

 might be added therefore that Aime accordingly distinguished 

 two groups of interstitial cells or two forms of 'gland:' (a) the 

 fetal, derived from the 'connective tissue;' (b) the adult, de- 

 rived from the theca interna. This grouping has been essentially 

 followed recently by Popoff ('11). Any discussion of the strict 

 applicability or value of these distinctions will not be entered 

 into now. It may be pointed out however that a full study of 

 the developmental history of the ovary and of the interstitial 

 cells in particular, has been made in no form save the cat, by 

 Saimont ('05) and v. Winiwarter and Saimont ('08). 



