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MANUAL OF HISTOLOGY. 



to be formed (puberty in man, rutting season in animals), most of the 

 glandular epithelium cells of the seminal tubules undergo division, by 

 which act a multitude of delicate, pale, and transparent elements of 

 spherical form are produced, with vesicular nuclei of 0'0056-0-0079 mm. 

 in diameter, sometimes single, sometimes ranging from 10 to 20. These 

 cells vary in diameter between O'OllS and 0*0074. 



From them the seminal filaments are supposed to be developed, and, 

 moreover, from the nuclei. At first it was thought that, in the interior 

 of each of these vesicular nuclei, a seminal element took its rise ; but 

 Koelliker asserted later that the whole nucleus becomes converted into a 

 spermatozoon. This he stated to take place by its becoming elongated 

 and flattened, and dividing into an interior dark and posterior lighter 

 portion, and sending out at one end a filament destined to increase more 

 and more in length, while the nucleus itself assumed gradually the char- 

 acteristic form of the head. 



The spermatozoa so formed were supposed to lie eventually within the 

 cells, in number corresponding to the original number of nuclei. Their 

 arrangement there was stated to be regular when more than a few were 

 present, namely, with their heads close to one another and the tails like- 

 wise parallel, bent according to the amount of space left to contain them. 

 A small number of these formative cells were supposed to rupture before 

 leaving the testis, setting free the spermatozoa; but by far the largest 

 proportion of the latter to be liberated in the epididymis. 



But these theories, the correctness of which was for some time believed 

 to be beyond doubt, have been since found to be untenable, and the 

 genesis of the spermatozoa is at the present day a point of great obscurity. 

 Henle was the first to point out, some years ago, another order of things 

 from that just mentioned. He found, namely, two kinds of cells in the 

 seminiferous tubuli, one with coarsely and another with finely granular, 

 sharply-defined, nuclei. He supposed the head to take its origin from the 

 latter, which project beyond the surface of the cells ; further, that the 

 filamentous process does not spring from the interior of the cell. In the 

 last view he is supported by Schweigger-Seidel. This observer regards the 

 spermatozoon as a single ciliated element formed 

 by the metamorphosis of a whole cell. The nuc- 

 leus, he believes, is transformed into the head, and 

 the middle portion to be derived from the remainder of 

 the cell-body, while the terminal filament represents 

 a cilium. According to Henle, cells with rolled-up 

 filaments never occur as normal structures in the 

 seminiferous tubes, which is also denied by both 

 Schweigger-Seidel and La Valett-St George, with 

 whom we also entirely agree. 



From our own, but, we must confess it, rather hasty, 

 observations (fig. 550), the process of the formation 

 of spermatozoa appears to be as follows : The nucleus 

 of the primary seminal cell (a) advances to the peri- 

 phery (b). Then the formation of the caudal appen- 

 dage commences (c). The nucleus then passes beyond 

 the original boundary of the formative cell, clothed 

 in a thin layer of protoplasm (d). Later still, the nucleus, -with this cover- 

 ing of protoplasm, forms the head of the seminal element, while the 

 appendage of the cell-body grows out into a long thread (e). Finally (/), 



Fig. 550. Mode of forma- 

 tion of spermatozoa in 

 the mammal. 1, head ; 

 2, middle portion; 3, 

 terminal filament. 



