** 3 -T .< 



652 THE HUMAN BODY. 



cells elongate, the nucleus remaining near the deeper end and 

 the protoplasm extending towards the lumen of the tubule, 

 into which it ultimately projects. Such cells are sperma- 

 toUasts, and lie in bunches side by side and several rows 

 deep. Interlaced among them are other granular supporting 

 cells of the epithelium, which are probably concerned with 

 the nutrition of the essential cells. The final step by which 

 the spermatoblast is converted into a spermatozoon is a kary- 

 okinetic division into two unequal cells: a part of the nu- 

 cleus with a little of the protoplasm separates and appears to 

 have no further function; the remaining part of the nucleus 

 (male pronucleus] remains as the head of the spermatozoon 

 and the cell protoplasm develops into the neck and tail. 

 The spermatozoa appear frequently to be cast off before 

 their development is completed : at least many spermato- 

 blasts which have not gone through the final stages are 

 found in the vasa recta, and even in the vas deferens. 

 Probably the secretion normally collects in the vesiculse 

 seminales, and there undergoes its final elaboration. 



The Reproductive Organs of the Female. Each ovary 

 (0, Fig. 187) is a dense oval mass about 3.25 cm. (1.5 inches) 

 in length, 2 cm. (0.75 inch) in width, and 1.27 cm. (0.5 inch) 

 in thickness; it weighs from 4 to 7 grams (60-100 grains). 

 The organs lie in the pelvic cavity enveloped in a fold of 

 peritoneum (the broad ligament), and receive blood-vessels 

 and nerves along one border. From time to time ova reach 

 the surface, burst through the enveloping peritoneum, and 

 are received by the wide fringed aperture, j#, of the oviduct 

 or Fallopian tube, od. This tube narrows towards its inner 

 end, where it communicates with the uterus, and is lined by 

 a mucous membrane, covered by ciliated epithelium; plain 

 muscular tissue is also developed in its wall. The uterus 

 (u, c, Fig. 187) is a hollow organ, with relatively thick mus- 

 cular walls (left unshaded in the figure); it contains the 

 foetus during pregnancy and expels it at birth; it lies in the 

 pelvis between the Trrhrary bladder and~fhe"rectum (Fig. 188); 

 the Fallopian tubes open into its anterior corners. It is free 

 above, but its lower end is attached to and projects into the 

 vagina. In the fully developed virgin state the organ rs 

 somewhat pear-shaped, but flattened from before back; about 

 7.5 cm. (3 inches) in length, 5 cm. (2 inches) in breadth at 

 its upper widest part, and 2.5 cm. (1 inch) in thickness; it 



