INTERSTITIAL CELLS OF MAMMALIAN OVARY 79 



substances of very distinct value to the organism as a whole, 

 would be as constant in its presence and development. 



Most biological problems, particularly those attempting to 

 explain the genetic significance of a structure or organ, possess 

 two quite distinct aspect ; (a) the determination of the processes 

 that underlie the structural appearance, their correlations and 

 explanation in terms of cause and effect, (b) the part they play 

 in the bodily economy — for the individual or the race; as com-" 

 monly expressed, the 'purpose' for which they exist, their 'func- 

 tion' in the organism; as the writer prefers to put it, their con- 

 tribution to the complex pattern of the bodily activities and 

 whose dominant component is adaptation. The existence of the 

 double character of developmental problems and the significance 

 of this, is not, I believe, sufficiently appreciated at the present 

 day. If it is possible to ascribe a 'function' to an organ, the end 

 and aim of its investigation is frequently believed to be attained, 

 without full comprehension of what has been gained in the de- 

 termination of 'function.' It is largely due to the dominance of 

 the conception of the animal organism as a colony of organs 

 each with its specific function or functions, that the interstitial 

 cells are seized upon as an internal secretory gland, because 

 there are no other cells in the ovary which meet the requirement 

 of 'gland cells.' It is I beheve the analogy of a superficial re- 

 semblance that here, as in other instances, has led to a false 

 morphological grouping. 



Apart from the question of the recognition of the interstitial 

 cells as a gland in the morphological sense, is the quite distinct 

 question as to whether they constitute a gland in the physiologi- 

 cal sense; that is, whether from them, as interstitial cells, come 

 substances formed as a result of their interstitial cell metabolism, 

 which reaching the circulation, produce characteristic effects in 

 other parts of the body. Any adequate consideration of this 

 question lies beyond the scope of this paper and outside any 

 morphogenetic study of the ovary. I desire therefore simply to 

 offer a few comments upon certain aspects only. The striking 

 characteristic of the interstitial cell is the large lipoid content. 

 This apparently consists of phosphatids, fats and cholesterol. 



