208 PHYSIOLOGY CHAP. 



influence the accumulation or loss of fat, which in not a few cases 

 manifests itself gradually, and only becomes definite after a long 

 lapse of time. 



To appreciate in their intimate nature the material changes 

 following bilateral ovariotomy the comparative researches carried 

 out on the dog before and after spaying are most important. 

 Loewy and Bichter (1899) determined the absorption of oxygen, 

 and the discharge of carbon dioxide, as a measure of the general 

 metabolism. They found that a few weeks after spaying .the 

 intensity of the metabolism gradually diminishes until it reaches 

 a definite minimum, when it remains constant. The diminution 

 of the respiratory gaseous exchange reaches about 20 per cent of 

 its initial value. 



This was observed by them in cases in which after ovariotomy 

 the weight of the body increased, as well as in those in which it 

 diminished ; in the first instances the lowering of respiratory 

 activity is absolute, and not only relative to the weight of the 

 body as in the second cases. 



This decrease in the respiratory exchange probably depends on 

 a diminution of the oxidation processes in the tissues, due to the 

 want of the continuous internal secretion of the ovaries. Loewy 

 relates that he kept a spayed bitch under observation for three 

 years and a half, and found that the minimum value reached by 

 the respiratory exchange remained almost constant for all this 

 long period. He noticed also that if ovarian extract was injected 

 under the skin of this animal, or of others similarly spayed, or the 

 substance of the ovaries of any animal whatever was administered 

 by the mouth, the activity of the respiratory exchange rose again 

 to normal, or even above it. The glycerine extract of the ovary 

 shows itself always more active than testicular extract ; the first 

 acts in castrated females as well as males, the second only in 

 males. The attempts directed to define more exactly and isolate 

 the active substance of the ovary, as that of the testicle, have not 

 led so far to any satisfactory results. 



The internal secretion of the ovaries appears also to have some 

 relation with the material changes in the bones. Fehling, in his 

 gynaecological clinic, had observed that the morbid process in the 

 bones known as osteomalacia improves noticeably after ovariotomy 

 (1895). He then ascertained the amount of lime and phosphorus 

 eliminated by those affected, both before and after spaying, but 

 did not find any sensible difference that would furnish an explana- 

 tion of the empirical fact observed. Curatolo and Tarulli, however 

 (1896), repeated in my laboratory the same researches on dogs, and 

 noticed that after bilateral ovariotomy there is a diminished 

 elimination of phosphorus, but that after injections of ovarian 

 extract there was an appreciable increase. Neumann, in the same 

 year, confirmed in the main particulars the observations of 



