764 HANDBOOK OP PHYSIOLOGY. 



go on for hours or days in the alkaline fluids of the body. It is stopped 

 by any of the agencies which stop ciliary movement, e.g.*, acids, or 

 strong alkalies, alcohol, chloroform, cold to C., and heat above 50 C. 



On examining the spermatozoon of Triton cristatus, one of the am- 

 phibia which possess the largest spermatozoa of all vertebrate animals, 

 H. Gibbes found that the organism consisted of (a) a long pointed head, 

 at the base of which is (#), an elliptical structure joining the head to 

 (c), a long filiform body; (d), a fine filament, much longer than the 

 body, is connected with this latter by (e), a homogeneous membrane. 



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 threadlike body, and the filament springs from it. 



While the spermatozoon is living, this filament is in constant mo- 

 tion; at first this is so quick that it is difficult to see it, but as its vital- 

 ity becomes impaired the motion gets slower, and it is then easily per- 

 ceived to be a continuous waving from side to side. 



The spermatozoa of all mammalia examined, consisting of man, bull, 

 dog, horse, cat, pig, mouse, rat, guinea-pig, had instead of the long-pointed 

 head of the amphibian, a blunt thick process of different shapes in the 

 different animals ; and from the root or neck of this proceeded the long 

 filament just as in the amphibia, only so delicate as to be invisible except 

 with very high powers. 



In man the head (fig. 459) is club-shaped, and from its base springs 

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

 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 sper- 

 matozoa of any other Mammal examined. 



From his investigation, Gibbes concluded : 1st, that the head of the 

 spermatozoon is inclosed 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 mesentery. 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 on by alkalies ; 

 these reagents have no effect, however, on the other part, exempting 

 the membraneous 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 at- 

 taching it to the body. 



