CAUSES OF ITS PRODUCTION. 55 



Having thus learned the structure and mode of formation of the corpora 

 lutea which are seen in impregnated animals we have now to enquire 

 whether such bodies are always produced as a consequence of the rupture 

 of Graafian follicles, and the discharge of their ova. This question must 

 undoubtedly, with some limitation, be answered in the affirmative, as far as 

 it regards quadrupeds in the state of heat. For even if the statements of 

 the older anatomists, who speak of having found corpora lutea in unim- 

 pregnated animals, were left out of consideration, the more recent observa- 

 tions of Sir E. Home, Dr. Blundell, M. Raciborski, and M. Bischoff, would 

 render it certain that the extrusion of ova from the Graafian follicles of 

 animals in heat, is attended with the formation of corpora lutea even when 

 the extruded ova do not become impregnated. In the figures, given by 

 Sir E. Home * and M. BischorT,f of corpora lutea formed under these cir- 

 cumstances, it is evident that the growth of the yellow substance has pro- 

 ceeded to such an extent as to protrude from the orifices of the ruptured 

 follicles, after filling their cavities. These are certainly corpora lutea 

 which could not be distinguished from corresponding bodies of the same 

 stage of development in the ovaries of impregnated animals. In the 

 impregnated animal, however, the corpus luteum continues to increase in 

 size after the orifice in the follicle has closed ; and whether this is the case 

 in animals which are not impregnated is doubtful. It is probable that if 

 the ova have not been fecundated, the state of orgasm of the ovaries and 

 Graafian follicles, which arose during the condition of heat, subsides, and 

 that the corpora lutea then, instead of continuing to grow, quickly shrivel 

 and disappear. For if it were not so, if the corpora lutea attained their 

 full size in unimpregnated animals, the ovaries of those animals in which 

 the period of heat recurs after short intervals, would constantly be found 

 to contain fully formed corpora lutea ; and this is not the case. 



With regard to the human female the limitations with which the rule 

 may be admitted are greater. There is reason to believe that under nor- 

 mal circumstances the rupture of a Graafian follicle and the discharge of an 

 ovum at the period of menstruation is attended with that change in the 

 tunic of the follicle which constitutes the first step in the formation of the 

 corpus luteum. For amongst the descriptions given by writers J of ruptured 

 Graafian follicles found in virgins and other menstruating women who 

 could not have been recently impregnated, there are several in which it is 

 distinctly stated that a layer of yellow substance existed in the walls of the 

 follicle ; and in other instances, bodies resembling in structure the corpora 

 lutea of pregnant women have been found in the ovaries of females who had 

 menstruated at some distance of time, and who had not been pregnant. 



* Lectures on Comparative Anatomy, vol. iv. t Ann. des Sc. Nat., 1844. 



Dr. Lee, Dr. Paterson, Dr. Ritchie, Renaud, op. citatis. 



Dr. Ritchie's case. x. part i. sec. ii. Medical Gazette, and Dr. Blundell's case, seem to 

 have been unquestionably of this nature. 



