The spermatozoids were considered as animalcules by Leuwenhoeck Haller, Spallanzani, Gleichen, Hill, Czermak, Valentin, Schwann, Pou chet and Pajot; but to-day they are regarded, not as animalcules, but as cellular elements. BiiHiker was the first to demonstrate that the sperma tozoids are not animalcules, and that they develop in a cell, and at the ex pense of the nucleus. Since then, Robin, Reichert, Leuckart, Acker mann, Funke, Henle and Godard have adopted the theory of Hiker, and it was only after 1864 that the question of spermatogenesis entered a new phase. At that time, Sertoli discovered in the seminiferous ducts of the rat peculiar cells with a large base, divided into lobes at their apex, and provided with a nucleus with a cylindrical prolongation. Since then, in 1875, Ebner and Neumann demonstrated that the spermatozoids develop at the expense of these prolongations, and the small lobes of the cells of Sertoli.
In 1800, Dr. Planteau reviewed the different theories that had existed, and showed that Hiker, studying the seminiferous tubes, proved that they are composed of a thin layer of laminar tissue, below which was an amorphous and absolutely hyaline layer, on which, in the adult, rested a polyhedral epithelium. These tubes end in a ccecum, towards the periphery of the testicles, having at great intervals small diverticuli, which also end in a ccecum, in which are found the pe culiar elements described by Robin under the name of male ova. Exte riorly, and laterally, Biker describes polygonal cells, of an epithelial appearance, which flatten each other, and which enclose a nucleus with a nucleolus. Within this first layer is a polyhedral epithelium and large cells with many nuclei.
Pouchet and Tourneux consider the testicular epithelium as formed: 1st. of special cells, which they called spermatoblasts ; 2d. of polyhedral cells interspersed among the spermatoblasts.
The spermatoblasts are elements presenting a flattened base, of a regu lar and polygonal shape, which is directly applied to the wall of the seminiferous tubes. This base, which presents a large nucleus, is sur mounted by a narrow portion, the swollen extremity of which is directed towards the lumen of the seminiferous tube. This extremity is divided into lobes which give birth to the spermatozoids. All the bases touch at the wall of the tube, and form, by their union, a very regular mosaic.
According to Bolliker the seminiferous tubes contain three kinds of cellular elements: 1st. cells with a single nucleus, which he considers as
epithelial 2d. Larger or smaller cells, containing a variable number of nuclei, and which he called mother cells. 3d. Vesicular elements, also containing nuclei, which he called spermatic cysts. In the mass of these nuclei, contained either in the mother cells or in the cysts, appears a thickening which forms the head and body of the spermatozoid. Attached to this thickening is a rolled-up filament, a filament that is nothing else than the tail. The body of the spermatic filaments comes from the nuclei of the seminal cell; the filaments spring from these nu clei themselves. The nucleus first lengthens at its poles into a delicate tube, which is then perforated by an opening at its extremity. The con tents of the nucleus form in the interior of the tube a conical corpuscle from which the filament springs.
According to Reichert, the spermatozoids proceed from vesicles that develop at the bottom of the seminiferous canals. These cells have a nu cleus. The contents of these cells become 'granular like the vitellus of the female ovum, then segment into a mass of cells, each of which is to form a spermatozoid. At one of tho poles of the cell appears a prolonga tion, the tail: the cell itself forms the head.
Robin, who adopted Reichert's ideas, compares the mother-cell of Reichert to a female ovum, and calls it the male ovum.
Godard shows that the spermatozoids come into existence at the ex pense of two elements contained in the seminiferous canals: the mother cells and smaller cells, called daughter-cells. The granulations which compose the latter coalesce at one point of the cell, which becomes more opaque, to form the head, then the other granules coalesce to form the tail. The spermatozoid, which is at first rolled up in the cell, becomes free by rupture of this latter, the tail then unrolls and the movements soon begin. This is the endogenetic theory. (Fig. 68).
The second theory is the theory of exogenetic formation.
We have seen that, according to Pouchet and Tourneux, the sperms toblasts are elements presenting a flattened base, of a regular, polygonal shape, and directly applied to the wall of the seminiferous tube. This base has a large nucleus, and is surmounted by a reduced portion, the enlarged extremity of which points towards the lumen of the seminiferous tube. This extremity divides into lobes from which spring the spermato zoids.