884 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



Maturation of the Spermatozoon. Considerable theoretical interest 

 attaches to the question as to the real morphological value of the spermatozoon. 

 It is undoubtedly a cell, and has arisen by division from one of the testicular 

 cells, called the primary spermatocyte or sometimes the mother-cell of the 

 spermatozoon. But is it the morphological equivalent of one of the mother- 

 cells ? In most animals, and probably also in man, each primary spermatocyte 

 gives rise to four spermatids, which grow directly into four spermatozoa. The 

 process of derivation of the spermatozoa may be called, by analogy with the 

 process in the ripening of the ovum, maturation. The details and essence of 

 the process have been much discussed. Van Beneden found in an interesting 

 worm, Ascaris, that the number of chromosomes in the nucleus of a single 

 spermatozoon is only half that in the original testicular cell ; that is, the pro- 

 cess of maturation of the spermatozoon consists in a reduction of the chromo- 

 somes by one half. This discovery has since been extended to many other 

 forms, including mammals and man, 1 and it has been shown further that the 

 mature spermatozoon contains only one-half the number of chromosomes cha- 

 racteristic of the tissue-cells of the species in question. In the light of the 

 subsequent process of fertilization these facts are interesting. Hertwig and 

 Weismann, who regard the chromatic substance of the nucleus as the bearer 

 of the hereditary qualities, interpret this halving of the chromatin as a pro- 

 vision for the reduction of the hereditary mass, which later will be restored to 

 its full amount by union with the egg. As we shall see, the maturation of 

 the ovum follows a somewhat similar course, and, since the process has been 

 more fully studied there, we shall reserve further discussion until that subject 

 is reached (p. 889). 



Semen. Semen consists of spermatozoa, together with fluid and dissolved 

 solids, coming partly from the testes themselves, but chiefly secreted by the 

 accessory sexual glands namely, the glands within the vasa deferentia, the 

 seminal vesicles, the prostate gland, and Cowper's glands. It is a whitish, 

 viscid, alkaline fluid, with a slight characteristic odor. The amount passed out 

 at any one time has been estimated at between 0.5 and 6 cubic centimeters. Its 

 chemical composition has not been examined exhaustively. Besides water, it 

 contains approximately 18 per cent, of solid substances, which comprise nuclein, 

 protamine, proteids, xanthin, lecithin, cholesterin, and other extractives, fat, and 

 sodium and potassium chlorides, sulphates, and phosphates. Under proper treat- 

 ment colorless crystals, called Charcot's crystals, may be obtained from semen. 

 They appear to be a phosphate of a nitrogenous base, which has been called sperm- 

 me. Interest in the semen centres in its histological rather than its chemical 

 features. The fluid portion serves as a vehicle for the transportation of and pos- 

 sibly also for the nutrition of the ripe spermatozoa. Colorless particles, called 

 seminal granules, exist in semen. They are possibly parts of nuclei of disin- 

 tegrated cells. Comparatively little is known of the composition or the specific 

 function of the individual secretions contributed by the various organs. The 

 disintegration of the nutritive cells of the testis probably furnishes some of the 



1 v. Bardeleben : loc cit. 



