FAETHER DEVELOPMENT OF THE TESTICLE. 815 



The distinction of sex begins to be perceptible in the internal organs 

 of the human eminyo in the seventh week, and becomes more apparent 

 in the eighth. The reproductive gland is from the first connected with 

 the Wolffian body, of which its blastema seems to be actually a part ; 

 and it remains attached to it, or after its disappearance to the structure 

 wliich occupies its place, by a fold of the peritoneal membrane, consti- 

 tuting the mesorchiura or mesovarium. Upper and lower bands fix 

 the Wolffian body ; the upper passing to the diaphragm may be named 

 the diaphragmatic ; the lower running down towards the groin from 

 the Wolffian duct, contains muscular fibres and constitutes the future 

 gubemaculum testis and round ligament of the uterus. 



The Testicle. — In male embryoes at the tenth week already seminal 

 canals are visible, being at first, according to Kolliker, entirely composed 

 of cells, but by the eleventh and twelfth weeks the tubes have become 

 somewhat smaller, longer, and are now branched and possess a mem- 

 brana propria. There is also by the end of the third month a com- 

 mencement of lobular division, and the body of the testis is now 

 covered with a condensed laj-er of fibrous tissue which forms the tunica 

 albuginea. 



In connection witli the development of the spermatic filaments or spennatozoa, 

 the essential part of the male reproductive element, previously referred to at 

 p. 448 of this volume, it may here fui'ther be stated that renewed researches by 

 Neumann (Ai'chiv filr Microsc. Anat., vol. xi., p. 292), appear to show that the 

 doubts thrown by Sertoli and Merckel on the statements of V. Ebner are not 

 well founded, that there really exist within the seminal ducts protoplasmic 

 columns stretching from within the wall of the tube into its cavity, and that the 

 spennatic filaments are produced in connection with the inner ends of the 

 columns as branched lobes, amounting- in general to ten or twelve in number, in 

 which the heads lie outwards imbedded in the protoplasmic stalk, and the fila- 

 ments or tails are directed inwards towards the central lumen of the tube. Each 

 stalk, or sjjcrmatohlant, as Neumann proposes to name it, possesses a large clear 

 nucleus with nucleolus, and previous to the formation of the heads there are 

 nuclei corresponding in number to them, which do not, however, appear to arise 

 directly from division of the main nucleus of the stalk, but rather to be formed 

 as free nuclei in the protoplasm. Each spermatozoon consists of three parts, 

 which are most easily disting-uished in those which have not reached their stage 

 of full development. These parts are, 1st, the head, or, as it may from its form 

 in some animals be called, the hook ; 2nd, the body or middle pai-t, forming a 

 slight thickening, and frequently of a vesicular appearance ; and 3rd, the fila- 

 ment or tail. The fii-st of these proceeds more immediately from a nucleus, the 

 second is the remains of the protoplasmic covering of a spennatoblastic lobe, the 

 feird is a ciliated production from the last. The bases of the spermatoblasts ai-e 

 attached to the inner sm-face of the fibrous coat of the seminal canals, to which 

 they furnish a complete lining, being set closely upon it like a layer of hexagonal 

 plates. The stalks rise as tapering processes from these plates, and in the inter- 

 vals between the stalks, necessarily largest towards the periphery, there is a 

 number of opaque gi-anular spherical cells, the exact nature of which is not 

 ascertained, but which it is conjectured may be the source of new sper- 

 matoblasts. 



An interesting view is presented by Neumann of the analogy of these spenna- 

 toblasts of the seminal tubes with the much elongated ciliated cells wliich are 

 found in the canals of the coni vasculosi and tube of the epididymis, in accord- 

 ance with which it may be held that the spermatic filaments are a peculiar forai 

 of ciliary structm-e, developed from protoplasmic elements of a cellular nature, but 

 v/hich undergo a peculiar modification in connection with the special destination. 

 cf the spermatozoa. 



