622 



SPECIAL HISTOLOGY. 



feri, the elements contained in them also increase in circumference ; 

 and when the formation of semen has actually commenced, they appear 

 as clear, round cells and cysts of 0-005-0-03 of a line, which, according 

 to their size, enclose a .variable number of, from 1 to 10, or even 20, 

 clear nuclei of 0-0025-0-0035 of a line with nucleoli. At this time, in 

 many cases, an epithelium is not manifest, the seminal tubes rather 

 appearing to be occupied entirely and solely by the cells in question ; 

 at other times, and particularly in advanced years, an epithelium is 

 presented containing fat, or pigment-cells, and surrounding the other 

 elements. The latter, Avhether they occur in the one way or the other, 

 are the precursors of the semen, which, in the mature condition, entirely 

 consists of an extremely small quantity of a viscid fluid, and of innu- 



Fig. 259. 



Fis. 260. 



merable minute, linear corpuscles having a peculiar movement, the 

 spermatic filaments or animalcules, fila spermatica, spermatozoa (also 

 spermatozoida). These spermatic filaments are perfectly homogeneous, 

 soft corpuscles, in which are distinguishable a thicker portion — the lody 

 or liead, — and a filamentary appendage, — the filament or tail. The 

 former is flattened and, viewed on the side, pyriform, with the acute 

 end in front ; on the surface oval, or even rounded anteriorly, and also, 

 though more towards the anterior part, slightly cupped ; so that it 

 sometimes appears clear in the middle, sometimes opaque. It is 0*0016— 

 0-0024 of a lino long, 0-008-0-0015 of a line wide, 0-0005-0-0008 of a 

 line thick, and according as it lies on the surface or edge, does it appear 

 clearer or more opaque, always presenting a peculiar fat-like, glistening 



Fig. 259. — Spermatic filaments (human); 1, magnified 350 diameters; 2, magnified 800 

 diameters; «, viewed on the edge; b, on the flat surface. 



Fig. 2G0. — Development of tlie spermatic filaments in the Rabbit: a, parent-cell (cyst) 

 with five nuclei: b, one with ten nuclei, each of which contains a convoluted spermatic fila- 

 ment ; c, an isolated nucleus with nucleoli ; c/, one with the spermatic filament ; e, a cyst with 

 a bundle of spermatic filaments; //. g g, immature spermatic filaments, with enlargements 

 in the filamentary portion ; A, a perfect spermatic filament, a, b. c. magnified 350 diameters ; 

 d — /(, magnified 500 diameters. 



