BIOLOGY IN HUMAN AFFAIRS 



between at least three parts of the ovary — the interstitial 

 tissue or framework, the follicles in which the eggs 

 develop, and the corpora lutea — not to mention the lining 

 of the uterus; and exact knowledge about these relations 

 has not been reached. It is in such matters that experimenta- 

 tion on higher animals must be relied upon to form a 

 background for the rare opportunities that permit direct 

 work on human beings in the course of surgical practice. 

 It has been found, in a few cases, that grafting a piece of 

 normal ovary so that it grows in the body of the patient 

 will cure abnormal and painful menstruation; but the 

 significance of such facts in detail can rarely be made out 

 unless the operation can be repeated with various modifica- 

 tions on animals. Zoologists are actively engaged in these 

 studies in certain laboratories where the necessary equip- 

 ment is provided; and they have developed a new branch 

 of technique, biological surgery, which enables them to 

 transfer living tissues from one animal into another, 

 perform operations on embryo mammals, observe the 

 condition of the reproductive organs at various times and 

 after specific treatments, remove single glands without 

 otherwise disturbing the animal, and in general carry out 

 ingenious and dangerous manipulations with a percentage 

 of success far greater than has been possible in the past. 

 This has made possible certain investigations on the 

 control of reproductive activity in the female, which are 

 now being quietly but actively pursued and which have 

 already yielded results that will, in all probability, have 

 great significance for human welfare. By the use of the 

 female hormones mentioned above, it is already possible 

 to render certain female animals either fertile or sterile 

 at will for given periods; and the successful application 

 of such methods to the human species can hardly be con- 

 sidered more than a mere matter of technique. With the 

 hormone material concentrated or isolated and thus 



[302] 



