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HAND-BOOK OF PHYSIOLOGY. 



The head, as it appears in the fresh specimen, has a different refrac- 

 tive power from that of the rest of the organism, and with a high power 

 appears to be a light green color; there is also a central line running up 

 it, from which it appears to be hollow. The elliptical structure at the 

 base of the head connects it with the long thread-like body, and the fila- 

 ment springs from it. Whilst the spermatozoon is living, this filament 

 is in constant motion; at first this is so quick that it is difficult to see it, 

 but as its vitality becomes impaired the motion gets slower, and it is then 

 easily perceived to be a continuous waving from side to side. 



In Man the head (Fig. 405) is club-shaped, and from its base springs 

 the very delicate filament which is three or four times as long as the 



FIG. 402. 



FIG. 403. 



FIG. 402. Plan of a vertical section of the testicle, showing the arrangement of the ducts. The 

 true length and diameter of the ducts have been disregarded, a, a, tubuli seminiferi coiled up in 

 the separate lobes; ft, tubuli recti or vasa recta; c, rete testis; d, vasa efferentia ending in the coni 

 vasculosi; , e, g, convoluted canal of the epididymis; 7i, vas deferens; /, section of the back part 

 of the tunica albuginea; i, t, fibrous processes running between the lobes; s, mediastinum. 



FIG. 403. Spermatic filaments from the human vas deferens. 1, magnified 350 diameters; 2, 

 magnified 800 diameters; a, from the side; ft, from above. (From Kolliker.) 



body; and the membrane which attaches it to the body is much broader, 

 and allows it to lie at a greater distance from the body than in the sperma- 

 tozoa of any other Mammal examined. 



Gibbes concludes: 1st. That the head of the spermatozoon is enclosed 

 in a sheath, which is a continuation of the membrane which surrounds 

 the filament and connects it to the body, acting in fact the part of a mes- 

 entery. 2ndly. That the substance of the head is quite distinct in its 

 composition from the elliptical structure, the filament and the long body, 

 and that it is readily acted upon by alkalies; these re-agents have no 

 effect, however, on the other part, excepting the membranous sheath. 

 3rdly. That this elliptical structure has its analogue in the Mammalian 

 spermatozoon; in the one case the head is drawn out as a long pointed 

 process, in the other it is of a globular form, and surrounds the elliptical 

 structure. 4thly. That the motive power lies, in a great measure, in 

 the filament and the membrane attaching it to the body. 



The occurrence of spermatozoa in the impregnating fluid of nearly all 

 classes of animals proves that they are essential to the process of impreg- 



