io 7 S REPRODUCTION 



the ovary for these functions is the corpus luteum, which is by some 

 investigators considered to be a gland with an internal secretion 

 (Born) . This secretion seems to be connected with the implantation 

 ot the ovum and the subsequent growth of both ovum and uterus 

 According to Fraenkel, the absence of the corpus luteum prevents 

 implantation. The experiments of Marshall and Jolly also indicate 

 that the corpus luteum forms some substance, which exerts an action 

 on the uterine mucosa, during the earlier stages of pregnancy. When 

 the ovum has not been fertilized the corpus luteum brings about 

 menstruation. Where fertilization has occurred it prepares the 

 uterus for the implantation of the ovum. Fraenkel considers that 

 there is no difference between the true and the false corpora lutea. 

 ' Lutein,' the dried extract of the corpora lutea of cows, is recom- 

 mended for the treatment of suppressed menstruation, and the 

 troublesome symptoms arising from the premature production of 

 the menopause by removal of the ovaries. 



The mode of origin of the corpus luteum has given rise to much 

 discussion. Two chief views have been put forward: (i) That it is 

 a structure derived from the connective-tissue wall (theca) of the 

 discharged follicle (v. Baer, etc.) ; (2) that it is developed from the 

 follicular epithelium (membrana granulosa) (Sobotta, etc.). The 

 second view seems to be best established. The granulosa cells 

 enlarge, it is said, without becoming more numerous. In certain 

 animals (guinea-pig), however, mitotic division of cells of the 

 membrana granulosa has been observed (L. Loeb). 



The influence of the ovary on the formation of the decidua has 

 been illustrated in a very interesting way by the investigations of 

 L. Loeb on the artificial production of deciduomata. He has shown 

 that if a number of incisions are made into the uterus of a rabbit or 

 guinea-pig within a certain interval after the cestral period (period of 

 heat), a structure with the histological characters of the decidua 

 develops at each wound. Impregnation does not appear to be a 

 necessary factor, nor even contact of the ovum with the uterine 

 mucous membrane. On the other hand, ovulation, the discharge oi 

 an ovum or ova, or at any rate the condition of the ovary associated 

 with this discharge, seems to be indispensable. For extirpation of 

 the ovaries in a large number of guinea-pigs prevented the formation 

 of deciduomata from wounds of the uterus made at the most favour- 

 able period after copulation. The uterus then appears to have an 

 inherent power of responding to such a stimulus as a mechanical 

 injury by the production of a decidual structure, but only under the 

 influence of the ovary. The ovarian factor is probably not nervous 

 but chemical, some specific substance which acts on the uterus 

 being liberated periodically in connection with the sexual rhythm. 



Development of the Ovum. Before fecundation, and apparently 

 as a preparation for it, the ovum is the seat of remarkable changes. 



