652 



HANDBOOK OF PHYSIOLOGY. 



Corpus Luteum of 

 Menstruation. 



Corpus Luteum of 

 Pregnancy. 



At the end of 



three iveeks . 



One month . 



Two months 



Six months . . 

 Nine months 



Three-quarters of an inch in diameter; central clot red- 

 dish; convoluted wall pale. 



Smaller; convoluted 

 wall bright yellow; 

 clot still reddish. 



Eeduced to the condi- 

 tion of an insignifi- 

 cant cicatrix. 



Absent. 



Larger; convoluted wall bright 

 yellow; clot still reddish. 



Seven-eighths of an inch in di- 

 ameter; convoluted wall bright 

 yellow; clot perfectly decolor- 

 ized. 



Still as large as at end of second 

 month; clot fibrinous; convo- 

 luted wall paler. 



Absent. One-half an inch in diameter; 



central clot converted into a 

 radiating cicatrix; the exter- 

 nal wall tolerably thick and 

 convoluted, but without any 

 bright yellow color. 



B. Of the Male. In order that the ovum should be fecundated or 

 impregnated, it is necessary that it should meet with the seminal fluid 

 of the male. This is accomplished by the junction of the sexes in the 

 act of coition, whereby the seminal fluid is discharged into the neigh- 

 borhood of, if not within, the cervix uteri. Before considering the 

 changes which are produced in the ovum by impregnation, it will be as 

 well to describe the nature of the seminal fluid. This consists essen- 

 tially of the semen secreted by the testicles : and to this are added, a 

 material secreted by the vesiculae seminales, as well as the secretion of 

 the prostate gland, and of Cowper's glands. Portions of these several 

 fluids are discharged, together with the proper secretion of the testicles. 



The semen is a viscid, whitish, albuminous fluid of a peculiar odor. 

 It contains epithelium, granules or colorless particles, and large num- 

 bers of spermatozoa, which are the characteristic and essential element. 

 The spermatozoa are minute bodies each consisting of a flattened oval 

 head and attached to it a long, slender, tapering, mobile flagellum or 

 tail. 



In some forms of spermatozoa there is a small middle piece inter- 

 posed between the head and the tail. The head is about -g-o^-jj-th inch 

 long and T o"J~o"oth ^ ncn broad. The tail is about -^oVo^h to ToWth inch 

 long. The spermatozoa possess the power of active movement, and it is 

 by this sinuous, cilia-like movement that they are propelled in the female 

 and so helped in their progress to meet the ovum. 



Spermatozoa. On examining the spermatozoon of Triton crista- 

 tus, one of the Amphibia which possess the largest spermatozoa of all 

 Vertebrate animals, Gibbes found that the organism consisted of (a) a 



